Methods and systems for supplying fuel to gas turbine engines

ABSTRACT

Methods and systems for supply of fuel for a turbine-driven fracturing pump system used in hydraulic fracturing may be configured to identify when the supply pressure of primary fuel to a plurality of gas turbine engines of a plurality of hydraulic fracturing units falls below a set point, identify a gas turbine engine of the fleet of hydraulic fracturing units operating on primary fuel with highest amount of secondary fuel available, and to selectively transfer the gas turbine engine operating on primary fuel with the highest amount of secondary fuel from primary fuel operation to secondary fuel operation. Some methods and systems may be configured to transfer all gas turbine engines to secondary fuel operation and individually and/or sequentially restore operation to primary fuel operation and/or to manage primary fuel operation and/or secondary fuel operation for portions of the plurality of gas turbine engines.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.15/929,768, filed May 21, 2020, titled “METHODS AND SYSTEMS FORSUPPLYING FUEL TO GAS TURBINE ENGINES”, which claims priority to and thebenefit of U.S. Provisional Application No. 62/704,395, filed May 8,2020, titled “METHODS AND SYSTEMS FOR SUPPLYING FUEL TO GAS TURBINEENGINES”, and U.S. Provisional Application No. 62/899,966, filed Sep.13, 2019, titled “METHODS AND SYSTEMS FOR AUTONOMOUS CONTROL OF A DUALFUEL MANAGEMENT SYSTEM”, the entire disclosures of all of which areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to methods and systems for supplying fuelto gas turbine engines, and more particularly, to methods and systemsfor controlling and/or managing the supply of a primary fuel from aprimary fuel source and a secondary fuel from a secondary fuel supply toa plurality of gas turbine engines associated with a hydraulicfracturing system.

BACKGROUND

Fracturing is an oilfield operation that stimulates production ofhydrocarbons, such that the hydrocarbons may more easily or readily flowfrom a subsurface formation to a well. For example, a fracturing systemmay be configured to fracture a formation by pumping a fracking fluidinto a well at high pressure and high flow rates. Some fracking fluidsmay take the form of a slurry including water, proppants, and/or otheradditives, such as thickening agents and/or gels. The slurry may beforced via one or more pumps into the formation at rates faster than canbe accepted by the existing pores, fractures, faults, or other spaceswithin the formation. As a result, pressure builds rapidly to the pointwhere the formation fails and begins to fracture. By continuing to pumpthe fracking fluid into the formation, existing fractures in theformation are caused to expand and extend in directions farther awayfrom a well bore, thereby creating flow paths to the well bore. Theproppants may serve to prevent the expanded fractures from closing whenpumping of the fracking fluid is ceased or may reduce the extent towhich the expanded fractures contract when pumping of the fracking fluidis ceased. Once the formation is fractured, large quantities of theinjected fracking fluid are allowed to flow out of the well, and theproduction stream of hydrocarbons may be obtained from the formation.

Prime movers may be used to supply power to a plurality of pumps forpumping the fracking fluid into the formation. For example, a pluralityof gas turbine engines may each be mechanically connected to acorresponding pump and operated to drive the pump. Some gas turbineengines may be designed to be operated using more than a single type offuel, which may provide efficiency and flexibility of use advantages ascompared to traditional fracturing pump fleets including engines thatare designed to be operated using a single type of fuel. Gas turbineengines designed to be operated using more than a single type of fuelmay also provide improved reliability, lower emissions, and/or smallerfoot print as compared to traditional fracturing pump fleets. In suchtraditional fleets, when an engine-pump unit runs low on fuel, such asdiesel fuel, that unit must be idled while refueling or while anotherstand-by unit is fueled and brought on-line.

For example, once low on fuel a traditional unit must be shut-off andrefueled while another unit is introduced into its place to make up forthe loss of the pumping power that the unit low on fuel provides. Thiscan affect the pumping performance during a fracturing operationsequence, as well as requiring human intervention to perform therefueling, aligning suction and discharge valves, etc. This can requiremultiple personnel to communicate information, for example, so therelatively complex process is performed correctly. Using a single fuelsource may also limit the ability for the fracturing fleet to complete afracturing operation sequence in an uninterrupted manner when low onfuel, which results in delays in pumping completion.

During a fracturing operation, the level of fuel available in each fueltank associated with a corresponding engine may need to be evaluatedbetween fracking stages to determine whether more fuel is required toensure that the units can be operated throughout the next stage ormultiple stages of the fracturing operation sequence. This may result inoperators needing to manually check fuel tanks and/or gauge levels,which can be time consuming and expose operators to hazardous liquidsand vapors.

Accordingly, it can be seen that a need exists for more efficient waysfor control and operation of fracturing pump systems. The presentdisclosure may address one or more of the above-referenced drawbacks, aswell as other possible drawbacks.

SUMMARY

According to a first embodiment, the present disclosure is generallydirected to methods and systems for control of fuel supplied to a gasturbine engine-driven fracturing pump system used in hydraulicfracturing. In some examples, a method of controlling fuel supply to aplurality of gas turbine engines connected to pumps associated with ahydraulic fracturing system may be provided. In some examples, themethod may include receiving a signal indicating that supply pressure ofprimary fuel supplied to one or more gas turbine engines of theplurality of gas turbine engines falls below a set point. The method mayfurther include initiating a timer and increasing a data sampling rateassociated with the plurality gas turbine engines based at least in parton the signal. In some examples, the method may further include, whenthe supply pressure of primary fuel to the one or more gas turbineengines remains below the set point when the timer reaches apredetermined end time, identifying a gas turbine engine of theplurality of gas turbine engines having a greatest amount of a secondaryfuel available. The method may further include causing supply of thesecondary fuel to the identified gas turbine engine in place of at leastsome of the primary fuel supplied to the identified gas turbine engine.

According to a further embodiment, this disclosure is also generallydirected to a system for controlling fuel supply to a plurality of gasturbine engines connected to pumps associated with a hydraulicfracturing system. The system may include one or more hydraulicfracturing units including one or more of the plurality of gas turbineengines and a pump connected thereto. The system may further include acontroller in communication with the one or more hydraulic fracturingunits. The controller may include memory including instructionsexecutable by a computer for performing operations that may include:receiving a signal indicating that supply pressure of primary fuel toone or more gas turbine engines of the plurality of gas turbine enginesfalls below a set point, and based at least in part on the signal,initiating a timer and increasing a data sampling rate associated withthe plurality of gas turbine engines. The operations may furtherinclude, when the supply pressure of primary fuel to the one or more gasturbine engines remains below the set point when the timer reaches apredetermined end time, identifying a gas turbine engine of theplurality of gas turbine engines having a greatest amount of a secondaryfuel available. The operations may further include causing supply of thesecondary fuel to the identified gas turbine engine in place of at leastsome of the primary fuel supplied to the gas turbine engine.

According to yet another embodiment, this disclosure is generallydirected to a system for supplying fuel to a plurality of gas turbineengines. The system may include a primary sensor associated with theplurality of gas turbine engines. The primary sensor may be configuredto generate a primary signal indicative of an ability of a primary fuelsource to supply an amount of primary fuel sufficient to operate theplurality of gas turbine engines at a first output. The system may alsoinclude a plurality of secondary sensors. Each of the plurality ofsecondary sensors may be associated with one of the plurality of gasturbine engines and may be configured to generate a secondary signalindicative of an amount of secondary fuel available from a secondaryfuel supply associated with each of the plurality of gas turbineengines. The system may further include a controller in communicationwith the primary sensor, each of the plurality of secondary sensors, anda plurality of primary valves. Each of the plurality of primary valvesmay be configured to control flow communication between the primary fuelsource and one of the plurality of gas turbine engines. The controllermay be configured to determine, based at least in part on the primarysignal, that the primary fuel source is supplying an insufficient amountof the primary fuel to operate one or more of the plurality of gasturbine engines at the first output. The controller may be furtherconfigured to determine, based at least in part on the secondarysignals, that the amount of secondary fuel available from a firstsecondary fuel supply associated with a first of the plurality of gasturbine engines is greater than an amount of secondary fuel availablefrom each of a remainder of the secondary fuel supplies associated witha remainder of the plurality of gas turbine engines. The controller mayalso be configured to cause a primary valve of the plurality of primaryvalves to inhibit flow communication between the primary fuel source andthe first of the plurality of gas turbine engines and cause supply ofsecondary fuel from the first secondary fuel supply to the first of theplurality of gas turbine engines.

According to still a further embodiment, this disclosure is generallydirected to a system for supplying fuel to a plurality of gas turbineengines. The system may include a primary sensor associated with theplurality of gas turbine engines. The primary sensor may be configuredto generate a primary signal indicative of an ability of a primary fuelsource to supply an amount of primary fuel sufficient to operate theplurality of gas turbine engines at a first output. The system may alsoinclude a controller in communication with the primary sensor and aplurality of primary valves, each of the plurality of primary valvesconfigured to control flow communication between the primary fuel sourceand one of the plurality of gas turbine engines. The controller may beconfigured to determine, based at least in part on the primary signal,that the primary fuel source does not have an ability to supply anamount of primary fuel sufficient to operate the plurality of gasturbine engines at the first output. The controller may be furtherconfigured to cause one or more primary valves configured to controlflow communication between the primary fuel source and the plurality ofgas turbine engines to inhibit flow communication between the primaryfuel source and the plurality of gas turbine engines. The controller mayalso be configured to cause supply of secondary fuel from a plurality ofsecondary fuel supplies to each of the plurality of gas turbine engines,wherein each of the plurality of secondary fuel supplies is associatedwith one of the plurality of gas turbine engines. The controller may befurther configured to cause operation of the plurality of gas turbineengines at the first output using the secondary fuel.

Still other aspects, embodiments, and advantages of these exemplaryembodiments and embodiments, are discussed in detail below. Moreover, itis to be understood that both the foregoing information and thefollowing detailed description provide merely illustrative examples ofvarious aspects and embodiments, and are intended to provide an overviewor framework for understanding the nature and character of the claimedaspects and embodiments. Accordingly, these and other objects, alongwith advantages and features of the present invention herein disclosed,will become apparent through reference to the following description andthe accompanying drawings. Furthermore, it is to be understood that thefeatures of the various embodiments described herein are not mutuallyexclusive and can exist in various combinations and permutations.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the embodiments of the present disclosure, areincorporated in and constitute a part of this specification, illustrateembodiments of the present disclosure, and together with the detaileddescription, serve to explain principles of the embodiments discussedherein. No attempt is made to show structural details of this disclosurein more detail than can be necessary for a fundamental understanding ofthe embodiments discussed herein and the various ways in which they canbe practiced. According to common practice, the various features of thedrawings discussed below are not necessarily drawn to scale. Dimensionsof various features and elements in the drawings can be expanded orreduced to more clearly illustrate embodiments of the disclosure.

FIG. 1 illustrates an example system for supplying fuel to an examplehydraulic fracturing system according to embodiments of the disclosure.

FIG. 2 is a schematic diagram of an example fuel distribution systemaccording to embodiments of the disclosure.

FIG. 3 is a schematic diagram of another example fuel distributionsystem according to embodiments of the disclosure.

FIG. 4 is a schematic diagram of yet another example fuel distributionsystem according to embodiments of the disclosure.

FIG. 5 is a schematic diagram of an example piping arrangement forsupplying primary fuel and secondary fuel to a gas turbine engineaccording to embodiments of the disclosure.

FIG. 6 is a block diagram of an example method for supplying fuel to aplurality of gas turbine engines according to embodiments of thedisclosure.

FIG. 7A is a block diagram of an example method for supplying fuel to aplurality of gas turbine engines according to embodiments of thedisclosure.

FIG. 7B is a continuation of the block diagram of FIG. 7A.

FIG. 8A is a block diagram of an example method for supplying fuel to aplurality of gas turbine engines according to embodiments of thedisclosure.

FIG. 8B is a continuation of the block diagram of FIG. 8A.

FIG. 9 is a schematic diagram of an example controller configured tocontrol supply of fuel to a plurality of gas turbine engines accordingto embodiments of the disclosure.

DETAILED DESCRIPTION

Referring now to the drawings in which like numerals indicate like partsthroughout the several views, the following description is provided asan enabling teaching of exemplary embodiments, and those skilled in therelevant art will recognize that many changes can be made to theembodiments described. It also will be apparent that some of the desiredbenefits of the embodiments described can be obtained by selecting someof the features of the embodiments without utilizing other features.Accordingly, those skilled in the art will recognize that manymodifications and adaptations to the embodiments described are possibleand can even be desirable in certain circumstances. Thus, the followingdescription is provided as illustrative of the principles of theembodiments and not in limitation thereof.

The phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. As used herein, theterm “plurality” refers to two or more items or components. The terms“comprising,” “including,” “carrying,” “having,” “containing,” and“involving,” whether in the written description or the claims and thelike, are open-ended terms, i.e., to mean “including but not limitedto,” unless otherwise stated. Thus, the use of such terms is meant toencompass the items listed thereafter, and equivalents thereof, as wellas additional items. The transitional phrases “consisting of” and“consisting essentially of,” are closed or semi-closed transitionalphrases, respectively, with respect to any claims. Use of ordinal termssuch as “first,” “second,” “third,” and the like in the claims to modifya claim element does not by itself connote any priority, precedence, ororder of one claim element over another or the temporal order in whichacts of a method are performed, but are used merely as labels todistinguish one claim element having a certain name from another elementhaving a same name (but for use of the ordinal term) to distinguishclaim elements.

FIG. 1 illustrates a schematic diagram of an example system 100 forcontrolling supply of fuel to an example hydraulic fracturing unit 102including a pump 104 configured to supply a fracking fluid to asubterranean formation, and a gas turbine engine (GTE) 106 connected tothe pump 104 and configured to drive the pump 104 according toembodiments of the disclosure. As shown in more detail with respect toFIGS. 2-4 . The system 100 may be part of a hydraulic fracturing systemthat includes a plurality (or fleet) of hydraulic fracturing unitsconfigured to pump a fracking fluid into a well at high pressure andhigh flow rates, so that a subterranean formation fails and begins tofracture in order to promote hydrocarbon production from the well.

In some examples, the system 100 may be semi-autonomously controlled orfully-autonomously controlled. In some examples, one or more of thehydraulic fracturing units 102 may include directly driven turbine (DDT)pumping units, in which the pumps 104 are connected to one or more GTEs106 that supply power to the respective pump 104 for supplying frackingfluid at high pressure and high flow rates to a formation. For example,a GTE 106 may be connected to a respective pump 104 via a reductiongearbox connected to a drive shaft, which, in turn, is connected to aninput shaft or input flange of a respective reciprocating pump 104.Other types of GTE-to-pump arrangements are contemplated. In someexamples, one or more of the GTEs 106 may be a dual-fuel or bi-fuel GTE,for example, capable of being operated using of two or more differenttypes of fuel, such as natural gas and diesel fuel, although other typesof fuel are contemplated. For example, a dual-fuel or bi-fuel GTE may becapable of being operated using a first type of fuel (e.g., a primaryfuel), using a second type of fuel (e.g., a secondary fuel), and/orusing a combination of a first type of fuel and a second type of fuel.The one or more GTEs 106 may be operated to provide horsepower to driveone or more of the pumps 104 to safely and successfully fracture aformation during a well stimulation project.

As shown in FIG. 1 , the system 100 may include a primary fuel source108 for suppling primary fuel to one or more of the GTEs 106 and, insome instances, a primary sensor 110 configured to generate one or moresignals indicative of an ability of the primary fuel source 108 tosupply an amount of primary fuel sufficient to operate the GTE 106 at adesired output. In some examples, for example, as shown in FIG. 1 , oneor more of the hydraulic fracturing units 102 may include a secondaryfuel supply 112 configured to supply a secondary fuel to one or more ofthe GTEs 106, for example, if the primary fuel source 108 is notsupplying a sufficient amount of fuel to the GTE 106 to operate the GTE106 at the desired output. In some examples, the hydraulic fracturingunit 102 may include a dedicated secondary fuel supply 112 for supplyingsecondary fuel to the GTE 106 of the respective hydraulic fracturingunit 102, for example, as shown in FIG. 1 . The system 100 may alsoinclude a secondary sensor 114 associated with the secondary fuel supply112 and configured to generate one or more signals indicative of anamount of secondary fuel available from the secondary fuel supply 112associated with one or more of the plurality of GTEs 106 associated witha hydraulic fracturing system, for example, a respective GTE 106associated with the respective secondary fuel supply 112, as shown inFIG. 1 . In some examples, one or more of the hydraulic fracturing units102 may include a plurality of the pump 104 and GTE 106 pairs. Althoughother types of fuel are contemplated, in some examples, the primary fuelmay include gaseous fuels, such as, for example, compressed natural gas(CNG), natural gas, field gas, pipeline gas, etc., and the secondaryfuel may include liquid fuels, such as, for example, diesel fuel (e.g.,#2 Diesel), bio-diesel fuel, bio-fuel, alcohol, gasoline, gasohol,aviation fuel, etc.

The system 100 may also include one or more controllers 116 configuredto control one or more embodiments related to the supply of fuel to oneor more of the GTEs 106 associated with one or more respective hydraulicfracturing units 102, for example, as outlined herein. In some examples,the system 100 may also include a remote terminal unit 118 incommunication with one or more of the primary sensor 110 or thesecondary sensor 114 and configured to provide a communication interfacebetween the primary sensor 110, the secondary sensor 114, and thecontroller 116. In some examples, the controller 116 may be configuredto interface with one or more of the remote terminal units 118associated with one or more of the hydraulic fracturing units 102. Theremote terminal units 118 may include communication and/or processinginterfaces, and may be configured to receive, store, and/or processsensor data associated with sensor signals received from one or more ofthe primary sensors 110 and/or one more of the secondary sensors 114, aswell as other sensors that may be associated with the system 100. Theone or more remote terminal units 118 may be configured to communicatesuch sensor data to the controller 116. In some examples, the controller116 may serve as a supervisory control for one or more of the remoteterminal units 118, one or more of which may be in communication with anindividual hydraulic fracturing unit 102 or multiple hydraulicfracturing units 102. The controller 116 and/or the remote terminalunits 118, in some examples, may include one or more industrial controlsystems (ICS), such as, for example, supervisory control and dataacquisition (SCADA) systems, distributed control systems (DCS), and/orprogrammable logic controllers (PLCs).

As shown in FIG. 1 , the GTE 106 is in communication with the primarysensor 110. In some examples, the primary sensor 110 may be configuredto generate one or more signals indicative of the fuel pressure of theprimary fuel (e.g., a gaseous fuel) supplied from the primary fuelsource 108 to the GTE 106, for example, the fuel pressure upstream ofthe GTE 106. This may be an indication of the ability of the primaryfuel source 108 to supply an amount of primary fuel sufficient tooperate one or more of the plurality of GTEs 106 at a desired powerand/or torque output. This may be an indication of the amount of primaryfuel available from the primary fuel source 108 for operating the GTE106 at the desired output. The primary sensor 110 may include one ormore pressure sensors and/or one or more flow meters. Other sensor typesare contemplated. For example, when the primary sensor 110 provides anindication of low pressure, the GTE 106 may not be able to operate atthe desired output. In some examples, under such circumstances, the GTE106 may be operated using the secondary fuel supplied by the secondaryfuel supply 112. The secondary fuel supply 112 may be provided in a fueltank or reservoir connected to the respective or associated GTE 106. Insome examples, when the primary fuel source 108 is not providing asufficient amount of the primary fuel to operate the respective GTE 106at the desired output (e.g., the fuel pressure is insufficient), atleast some or all of the primary fuel supplied to the GTE 106 may besupplemented and/or replaced with secondary fuel supplied by thesecondary fuel supply 112 associated with the respective GTE 106, forexample, as outlined herein.

The secondary sensor 114 may include one or more sensors configured togenerate one or more signals indicating the amount (e.g., the volume) ofsecondary fuel contained in the secondary fuel supply 112 of theassociated hydraulic fracturing unit 102. For example, the secondarysensor 112 may be configured to generate one or more signals indicativeof a level or volume of secondary fuel (e.g., diesel fuel) available forsupply to the GTE 106 in the secondary fuel supply 112 associated withthe hydraulic fracturing unit 102. In some examples, the secondarysensor 114 may include one or more sensors, such as, for example, aRADAR level sensor, a guided-wave RADAR level sensor, an ultrasoniclevel sensor, a capacitive level sensor, a hydrostatic level sensor, aprobe-type level sensor, a float-type level sensor, a radio frequencyadmittance level sensor, an electro-optical level sensor, and/or anyother type of sensor configured to generate signals providing anindication of the amount of secondary fuel available in the respectivesecondary fuel supply 112.

As shown in FIG. 1 , the controller 116 may, in some examples, be incommunication with the hydraulic fracturing unit 102 (e.g., the GTE 106and/or any related components) via a communications link 120 configuredto receive operational data from the hydraulic fracturing unit 102. Insome examples, communications may be performed according tocommunication protocols, such as, for example, Profibus, Modbus, andCANopen. The communications link 120 may be any of one or morecommunication networks, such as, for example, an Ethernet interface, auniversal serial bus (USB) interface, and/or a wireless interface. Insome examples, the controller 116 may be in communication with thehydraulic fracturing unit 102 via hard-wired link or cable, such as, forexample, a communications interface cable.

The controller 116 may include a computer system having one or moreprocessors configured to execute computer-executable instructions toreceive and/or analyze data from various data sources, such as thehydraulic fracturing unit 102, one or more primary sensors 110 and/orone or more secondary sensors 114, and may include one or more remoteterminal units 118. The controller 116 may be further configured toprovide inputs, gather transfer function outputs, and/or transmitinstructions from any number of operators and/or personnel. In someexamples, the controller 116 may be configured to perform controlactions, as well as provide inputs to the one or more remote terminalunits 118. In some examples, the controller 116 may be configured tocontrol, based at least in part on data received from one or more datasources (e.g., the hydraulic fracturing units 102, the primary sensors110, and/or the secondary sensors 112), one or more of various actionsto be performed by various controllable components of the hydraulicfracturing unit 102 and related components. In some examples, thecontroller 116 may be an independent entity or component communicativelycoupled to one or more remote terminal units 118.

FIG. 2 is a schematic diagram of an example fuel distribution system 200associated with a plurality, or fleet, of example hydraulic fracturingunits 102 according to embodiments of the disclosure, identified as 102a, 102 b, 102 c, 102 d, 102 e, 102 f, 102 g, and 102 h, although feweror more hydraulic fracturing units are contemplated. In the exampleshown, each of the plurality hydraulic fracturing units 102 includes aGTE 106, identified respectively as 106 a, 106 b, 106 c, 106 d, 106 e,106 f, 106 g, and 106 h. Each of the GTEs 106 supplies power for each ofthe hydraulic fracturing units 102 to operate a pump 104, identifiedrespectively as 104 a, 104 b, 104 c, 104 d, 104 e, 104 f, 104 g, and 104h. The example shown in FIG. 2 includes a manifold 202 configured tointegrate the fluid outputs (e.g., the fracking fluid outputs) of one ormore of the hydraulic fracturing units 102 to provide flow communicationwith the wellhead 204, which provides flow communication with thesubterranean formation being conditioned by the fracturing process.

The example fuel distribution system 200 shown in FIG. 2 is a hybridhub-type fuel distribution system, including a first primary fuel source108 a and a second primary fuel source 108 b. The example first andsecond primary fuel sources 108 a and 108 b are shared across theplurality of GTEs 106 in the plurality of hydraulic fracturing units102. In the example shown, a primary sensor 110 is associated with eachof the respective GTEs 106, and the primary sensors are respectivelyidentified as 110 a, 110 b, 110 c, 110 d, 110 e, 110 f, 110 g, and 110h. In some examples, each of primary sensors 110 may be configured togenerate one or more signals indicative of an ability of the primaryfuel source 108 a and/or 108 b to supply a sufficient amount of aprimary fuel (e.g., a gaseous fuel) to operate one or more of therespective GTEs 106 at a desired output (e.g., the desired output foreach of the GTEs 106 and/or the desired output total for all of theoperational GTEs 106). For example, the primary sensors 110 may includeone or pressure sensors and/or one or more flow rate sensors.

In some examples, the hybrid hub-type arrangement shown in FIG. 2 mayprovide flexibility of operation, for example, if one of the primaryfuel sources 108 a or 108 b fails to supply a sufficient amount ofprimary fuel to operate all the GTEs 106 at a desired output. The otherprimary fuel source may be able to partially or completely overcome anydeficit of the amount of primary fuel supplied by the underperformingprimary fuel source. However, such a hybrid hub-type arrangement mayrequire more set-up time, additional connections, and capital cost, forexample, due to additional piping and/or valves sometimes characteristicof such arrangements.

As shown in the example of FIG. 2 , each hydraulic fracturing unit 102includes a secondary sensor 114, identified respectively as 114 a, 114b, 114 c, 114 d, 114 e, 114 f, 114 g, and 114 h. The secondary sensors114 may be configured to generate one or more signals indicative of theamount of secondary fuel available from the respective secondary fuelsupplies 112 associated with each of the plurality of GTEs 106. Asdiscussed herein, signals generated by the secondary sensors 114 may bereceived by the controller 116 (see FIG. 1 ).

FIG. 3 is a schematic diagram of another example fuel distributionsystem 300 according to embodiments of the disclosure. The example fueldistribution system 300 shown in FIG. 3 , may be provided in associationwith a plurality or fleet of hydraulic fracturing units 102, forexample, at least similar to the plurality of hydraulic fracturing units102 shown in FIG. 2 . The example fuel distribution system 300 is amultiple hub and spoke-type system, which may include a dedicated firstprimary fuel source hub 302 a and/or a second primary fuel source hub302 b that provides primary fuel to each set of hydraulic fracturingunits 102 a-102 h. As indicated, dedicated supply lines identifiedrespectively as 206 a, 206 b, 206 c, 206 d, 206 e, 206 f, 206 g, and 206h, provide primary fuel to each respective hydraulic fracturing unit 102a-102 h. This example arrangement may provide relatively reducedflexibility in terms of sharing primary fuel across the first and secondprimary fuel source hubs 302 a and 302 b, but may provide substantiallyuniform piping pressure drops to all the hydraulic fracturing units 102a-102 h and may be desired in certain situations based on layout andconfiguration of the site.

FIG. 4 is a schematic diagram of yet another example fuel distributionsystem 400 provided in association with a plurality or fleet ofhydraulic fracturing units 102 according to embodiments of thedisclosure, for example, at least similar to those shown in FIGS. 2 and3 . The example fuel distribution system 400 shown in FIG. 4 is a daisychain-type arrangement and includes two dedicated primary fuel sources108 a and 108 b, each providing a single primary fuel supply connectionto two subsets of the hydraulic fracturing units 102 a-102 d and 102e-102 h, respectively. This example arrangement may provide relativelyreduced flexibility of operation and relatively higher fuel pressurevariability across hydraulic fracturing units 102 a-102 h, but may berelatively more cost effective, for example, because each set ofhydraulic fracturing units 102 a-102 h may be served by a single pipingconnection from the respective primary fuel sources 108 a and 108 b.

The exemplary fuel distribution systems 200, 300, and 400 depicted inFIGS. 2-4 are not intended to limit the arrangements or configurationsthat may be used in association with the hydraulic fracturing units 102of the system 100. One skilled in the art will appreciate that thechoice of fuel distribution system configuration may depend on a numberof factors, such as site layout, capital cost, and/or operation costconsiderations, among other factors.

FIG. 5 is a schematic diagram of an example piping arrangement 500 forsupplying primary fuel and secondary fuel to a GTE 106 according toembodiments of the disclosure. In the example shown, the GTE 106includes or is associated with a GTE fuel manifold 501 configured toaccept either or both primary fuel from the primary fuel source 108 andsecondary fuel from the secondary fuel supply 112 for operation of theGTE 106 using, in some examples, the primary fuel, the secondary fuel,or a combination of both the primary fuel and the secondary fuel. In theexample shown, the piping arrangement 500 includes a fuel line 502 forproviding flow communication between the primary fuel source 108 and theGTE fuel manifold 501. The piping arrangement 500 can be utilized in thesystem 100 in combination with a fuel distribution system, such as, forexample, any one of the example fuel distribution systems 200, 300, or400 shown in FIGS. 2-4 , and/or or other types of fuel distributionsystems. For example, the fuel line 502 may supply primary fuel from oneor more of the primary fuel sources shown in FIGS. 2-4 to the GTE 106associated with one of the hydraulic fracturing units 102.

Between the primary fuel source 108 and the GTE fuel manifold 501, afilter 504 is provided and configured to filter particulates, water,and/or other fuel contaminates from the primary fuel upstream of the GTEfuel manifold 501 to reduce the likelihood of, or prevent, damage to theGTE 106. The filter 504 may be a coalescing filter, although other typesof filters are contemplated, for example, depending on the particulatesand contamination expected in the primary fuel and/or the fuel line 502.

In the example piping arrangement 500 shown in FIG. 5 , a first primarysensor 110 (e.g., a pressure transducer) is provided upstream of the GTE106, and a second primary sensor 110′ (e.g., a pressure transducer) isprovided downstream of the filter 504. In some examples, the firstprimary sensor 110 and the second primary sensor 110′ may be configuredto generate one or more signals indicative of the fuel pressure at eachof the first primary sensor 110 and the second primary sensor 110′. Thecontroller 116 may be configured to receive the one or more signals anddetermine a fuel pressure drop across the filter 504. In some examples,if the pressure drop across the filter 504 rises above a pressure dropset point, it may be an indication that the filter 504 is at leastpartially obstructed or clogged, which may prevent the GTE 106 fromreceiving a sufficient amount of the primary fuel to operate at adesired output (e.g., full capacity), for example, if the fuel pressureis insufficient or is below a minimum threshold required for operationat the desired output.

In some examples, if this situation is encountered, the controller 116may be configured to cause the GTE 106 to operate using secondary fuelfrom the secondary fuel supply 112 instead of operating the GTE 106using primary fuel from the primary fuel source 108. For example, thecontroller 116 may communicate with a primary valve 506 and cause theprimary valve 506 to close, thereby shutting off fuel flow from theprimary fuel source 108 to the GTE 106. (FIG. 5 shows the primary valve506 in an open condition.) The controller 116 may also communicate witha pump 508 between the secondary fuel supply 112 and/or a secondaryvalve 510 (shown in an open condition) and cause the pump 508 to operateto supply secondary fuel from the secondary fuel supply 112 through thesecondary valve 510 in the open condition to the GTE 106. In someexamples, the controller 116 may communicate with the secondary valve510 to cause the secondary valve 510 to open and provide flowcommunication between the secondary fuel supply 112 and the GTE fuelmanifold 501, thereby switching operation of the GTE 106 from usingprimary fuel from the primary fuel source 108 to operation usingsecondary fuel from the secondary fuel source 112, which may beassociated with the hydraulic fracturing unit 102 to which the GTE 106is coupled. This may facilitate continued operation of the GTE 106 usingthe secondary fuel while the filter 504 is serviced (e.g., cleaned,flushed, and/or unclogged) and/or replaced. As shown in FIG. 5 , thepiping arrangement 500 may also include a filter 512 between thesecondary fuel supply 112 and the GTE fuel manifold 501 and configuredto filter particulates, water, and/or other fuel contaminates from thesecondary fuel upstream of the GTE 106 to reduce the likelihood of, orprevent, damage to the GTE 106. In some examples, a second primary valve506′ (shown in the open condition in FIG. 5 ) may be provided to preventsecondary fuel from flowing to the filter 504 by changing to a closedcondition when secondary fuel is supplied to the GTE 106. In someexamples, a secondary sensor 110″ may be provided between the secondaryvalve 510 and the GTE fuel manifold 501 and may be configured togenerate signals indicative of fuel pressure associated with thesecondary fuel upstream of the GTE fuel manifold 501.

In some examples, the system 100 may be configured to supply fuel to aplurality or fleet of GTEs 106 connected to respective pumps 104associated with a hydraulic fracturing system including a plurality orfleet of hydraulic fracturing units 102. One or more of the GTEs 106 maybe configured to routinely operate using a supply of primary fuelsupplied by a primary fuel source 108. The operation of the hydraulicfracturing units 102 including the GTEs 106 may be controlled via thecontroller 116. In some examples, the hydraulic fracturing units 102and/or GTEs 106 may be semi-autonomously or fully-autonomouslycontrolled via the controller 116. The controller 116 may include memorythat contains computer-executable instructions capable of receivingsignals from one or more of the primary sensors 110 and/or one or moreof the secondary sensors 114 associated with each of the hydraulicfracturing units 102.

For example, one or more of the primary sensors 110 may generate one ormore signals indicative that the one or more of the primary fuel sources108 is not supplying a sufficient amount of primary fuel to operate oneor more of the GTEs 106 at a desired output. In some examples, this maybe an indication that the fuel pressure or fuel flow rate to one or moreof the GTEs 106 is insufficient. For example, the one or more signalsmay provide an indication that the fuel pressure associated with one ormore of the GTEs 106 falls below a set point (e.g., a previously definedset point). For example, if the fuel pressure of the supply of primaryfuel for normal operation at a desired output is 250 pounds per squareinch gauge (psig), and the fuel pressure drops below a low-end set pointof, for example, 180 psig, the primary sensor 110 may be configured togenerate one or more signals providing an indication of the low fuelpressure condition, and based at least in part on the one or moresignals, the controller 116 may be configured to determine the low fuelpressure condition and generate an alarm indicating the low fuelpressure condition. In some examples, the controller 116 may beconfigured to initiate a timer and increase a data sampling rateassociated with sensor data received from one or more of the primarysensors 110 and/or one or more of the secondary sensors 114 associatedwith one or more of the GTEs 106 experiencing a lower fuel pressure thanrequired to operate at the desired output. For example, if the normaldata sampling rate for data from the primary sensors 110 and/or thesecondary sensors 114 is 500 milliseconds, the data sampling rate may beincreased to 250 milliseconds after receipt of a signal providing anindication that the fuel pressure is below the low-end set point. Insome examples, the data sampling rate may be increased by a factor of,for example, 1.5, 2, 3, 4, or 5.

In some examples, indication of fuel pressure falling below the low-endset point may be based on a primary fuel pressure process. For example,the primary pressure data from the primary sensors 110 may be collectedand sub-divided into two sample blocks. In some examples, the samplingrate increase, as described above, may be implemented when twoconsecutive sample blocks meet any one of the following criteria: 60% ofthe sample blocks drop a predetermined amount X below the low-end setpoint, or 40% of the sample blocks drop Y psi below the low-end setpoint. The values provided above are examples, and other values arecontemplated. Actual values of sample blocks as well as the values of Xand Y may be determined based on field testing or by other empiricaland/or theoretical (e.g., mathematical) methods. In some examples, thethreshold (or set-point) may be configurable via revisions of thecontrol system logic and function blocks within the logic.

If the fuel pressure of primary fuel, as indicated by one or more of theprimary sensors 110, remains below the low-end set point after the timerhas reached a predetermined end time, the controller 116 may beconfigured to identify the hydraulic fracturing unit 102 having thegreatest supply of secondary fuel (e.g., the greatest supply of dieselfuel) in its associated secondary fuel supply 112 (e.g., fuel tank).This identification may be performed based at least partially on inputfrom the secondary sensors 114, which may be configured to indicate alevel or volume of secondary fuel in a respective secondary fuel supply112. In some examples, once the controller 116 identifies the hydraulicfracturing unit 102 having the greatest amount of secondary fuel in itsassociated secondary fuel supply 112, the controller 116 may inhibitflow communication (or cease flow communication) between the primaryfuel source 108 and the GTE 106 associated with the primary sensor 110indicating insufficient fuel pressure and in some instances, causesecondary fuel in the secondary fuel supply 112 associated with the GTE106 to be supplied to the GTE 106 to supplement or replace the primaryfuel supplied to the GTE 106, such that the GTE 106 may operate at thedesired output using the secondary fuel in place of the primary fuel. Insome examples, the controller 116 may be configured to perform thisprocess semi- or fully-autonomously.

In some examples, the controller 116 may be configured to determinewhether any of the remaining GTEs 106 are being supplied with primaryfuel at an insufficient level (e.g., at an insufficient fuel pressure)associated with the remaining GTEs 106 of the remaining hydraulicfracturing units 102 of the plurality or fleet of hydraulic fracturingunits 102. In some examples, the above-outlined example process may berepeated for one or more (e.g., all) of the remaining hydraulicfracturing units 102. In a fracturing system including a plurality ofhydraulic fracturing units 102, if the pressure of the primary fuelsupplied to the hydraulic fracturing units 102 remains below thedesignated set point for more than one hydraulic fracturing unit 102after the first hydraulic fracturing unit 102 has been switched from anoperation using primary fuel to an operation using secondary fuel, theremaining hydraulic fracturing units 102 having the greatest amount ofsecondary fuel remaining in the respective secondary fuel supply 112will be switched (e.g., via the controller 116) from operation usingprimary fuel to operation using secondary fuel. In some examples, ifmore than 50% of the hydraulic fracturing units 102 are operating usingsecondary fuel, the controller 116 and/or the associated remote terminalunits 118 may be configured to cause one or more of the hydraulicfracturing units 102 to cycle through operating using secondary fuel tomaintain the desired level of output, for example, until the secondaryfuel supplies 112 reach a point at which the level of secondary fuelremaining in the respective secondary fuel supply 112 falls to, forexample, 10% or less of the capacity of a fuel tank containing thesecondary fuel supply 112. At this point, in some examples, thecontroller 116 may be configured to discontinue operation of all thehydraulic fracturing units 102 operating using secondary fuel, such thatonly hydraulic fracturing units 102 operating using primary fuel remainoperating.

In some examples, once a hydraulic fracturing unit 102 is switched tooperation using secondary fuel, the hydraulic fracturing unit 102 mayremain operating using secondary fuel, for example, until one of thefollowing two conditions are met: (1) the hydraulic fracturing unit 102has used more than a predetermined amount its secondary fuel supply 112,or (2) the fuel pressure of the primary fuel returns to a desiredoperating pressure (e.g., a fuel pressure above the low-end set point).When the first condition is determined by the controller 116, thecontroller 116 may be configured to switch operation of a different oneor more of the hydraulic fracturing units 102 from operation usingprimary fuel to operation using secondary fuel and switch the initialhydraulic fracturing unit 102 from operation using secondary fuel tooperation using primary fuel. For example, the predetermined amount maybe, for example, 30% capacity or less, 25% capacity or less, 20%capacity or less, or 15% or less capacity. When the second condition isdetermined by the controller 116, the controller 116 may receive one ormore signals from a corresponding primary sensor 110 indicating that thefuel pressure of primary fuel supplied to the hydraulic fracturing unit102 is above a high set point. In some such instances, the controller116 may be configured to initiate a second timer, and when the fuelpressure of primary fuel continues to be above the high set point afterthe second timer has elapsed, the controller 116 may be configured tocause the hydraulic fracturing unit 102 to operate using the primaryfuel from the primary fuel source 108 instead of operating usingsecondary fuel from the corresponding secondary fuel supply 112. Thecontroller 116 may be configured to thereafter return the data samplingrate to the original data sampling rate used when primary fuel issupplied from the primary fuel source 108, for example, during standardoperation.

In some examples, for the hydraulic fracturing units 102 operating usingsecondary fuel, the controller 116 may be configured to monitorsecondary fuel levels of the corresponding secondary fuel supplies. Whenthe controller 116 receives a signal indicating that the secondary fuellevel in the corresponding secondary fuel supply is below a minimumsecondary fuel level set point, the controller 116 may be configured tocause the hydraulic fracturing unit 102 to cease operation.

Similarly, in some examples, the controller 116 may be configured todetermine, based at least in part on a primary signal received from oneor more of the primary sensors 110, that the primary fuel source 108 issupplying an insufficient amount of primary fuel to operate one of theplurality of GTEs 106, or more of the GTEs 106, at the desired output(e.g., full capacity output). For example, a primary sensor 110associated with one or more of the plurality of GTEs 106 (e.g., aprimary sensor 110 associated with each of the GTEs 106) may beconfigured to generate a primary signal indicative of an ability of aprimary fuel source 108 to supply an amount of primary fuel sufficientto operate the plurality of GTEs 106 (e.g., each of the GTEs 106) at adesired output may generate one or more signals indicative of a fuelpressure, and the controller 116 may receive the one or more signals anddetermine whether the fuel pressure has fallen below a predetermined setpoint, which may correspond to a previously determined supply pressureconsistent with an inability of one or more of the GTEs 106 to operateat a desired output using the primary fuel from the primary fuel source108.

The controller 116, in some examples, may be configured to furtherdetermine, based at least in part on secondary signals generated by thesecondary sensors 114 indicative of an amount of secondary fuelavailable from the secondary fuel supplies 112 associated with each ofthe plurality of GTEs 106, that the amount of secondary fuel availablefrom a first one of the secondary fuel supplies 112 associated with afirst of the plurality of GTEs 106 is greater than an amount ofsecondary fuel available from each of a remainder of the secondary fuelsupplies 112 associated with a remainder of the plurality of GTEs 106.For example, a plurality of secondary sensors 114, each of which isassociated with one of the plurality of GTEs 106, may be configured togenerate a secondary signal indicative of an amount of secondary fuelavailable from a secondary fuel supply 112 associated with each of theplurality of GTEs 106. The secondary sensors 114 may generate the one ormore secondary signals, and the controller 116 may be configured toreceive the secondary signals and determine or identify, based at leastin part on the secondary signals, that a first one of the secondary fuelsupplies 114 associated with a corresponding first one of the pluralityof GTEs 106, has a greater amount of secondary fuel available than theremaining secondary fuel supplies 114 associated with each of the otherremaining GTEs 106.

In some examples, under such circumstances, the controller 116 may beconfigured to cause a primary valve 506 (see FIG. 5 ) of the pluralityof primary valves 506 to inhibit flow communication between the primaryfuel source 108 and the first of the plurality of GTEs 106. For example,each of a plurality of primary valves 506 may be provided and configuredto control flow communication between the primary fuel source 108 andone of the plurality of GTEs 106. The controller 116 may communicatewith one or more primary valves 106 associated with the first GTE 106and cause the one or more primary valves 506 to close, therebyinhibiting or shutting-off flow communication between the primary fuelsource 108 and the first GTE 106. In some examples, this may beperformed gradually, for example, as explained below. In some examples,the GTE fuel manifold 501 may begin switching to operation using thesecondary fuel prior to the one or more primary valves 506 closing. Forexample, secondary fuel from the secondary fuel supply 112 may alreadybe in flow communication with the GTE fuel manifold 501, and the GTEfuel manifold 501 may be configured to begin switching to usingsecondary fuel prior to the one or more primary valves 506 closing.

The controller 116 may also be configured to cause a supply of secondaryfuel from a first secondary fuel supply 112 associated with the firstGTE 106 to supply secondary fuel to the first GTE 106. For example, thecontroller 116 may communicate with a pump 508 (see FIG. 5 ) configuredto pump the secondary fuel from a secondary fuel supply 112 associatedwith the first GTE 106, and cause the pump 508 to operate by activatingthe pump 508. In some examples, the controller 116 may also communicatewith a secondary valve 510 (see FIG. 5 ) configured to control flowcommunication between the secondary fuel supply 112 and the first GTE106, and cause the secondary valve 510 to open, thereby permittingsecondary fuel to be supplied to the first GTE 106. This may beperformed gradually, for example, before and/or during closing of theprimary valve 506, which results in switching operation of the first GTE106 from primary fuel to secondary fuel. In some examples, this may beperformed prior to, concurrently, substantially simultaneously, and/orfollowing shutting-off flow of the primary fuel to the first GTE 106.

After causing the primary valve 506 to inhibit flow communicationbetween the primary fuel source 108 and the first of the GTEs 106, basedat least in part on the primary signal, the controller 116 may beconfigured to determine whether the primary fuel source 108 is supplyinga sufficient amount of the primary fuel to operate the remainder of theplurality of GTEs 106 at the desired output (e.g., at full capacity ofeach of the GTEs 106). In some examples, this may include the controller116 receiving primary signals from one or more of the primary sensors110 (e.g., all of the primary sensors 110 associated with each of theremaining GTEs 106) and determining whether any of the remaining GTEs106 are receiving insufficient primary fuel to operate at the desiredoutput. In some examples, one or more of such primary signals may beindicative of an insufficient fuel pressure.

In some examples, if the controller 116 determines that the primary fuelsource 108 is not supplying a sufficient amount of the primary fuel tooperate the remainder of the plurality of GTEs 106 at the desiredoutput, the controller 116 may be configured to determine, based atleast in part on the secondary signals from the secondary sensors 114,that the amount of secondary fuel available from a second secondary fuelsupply 112 associated with a second of the plurality of GTEs 106 isgreater than an amount of secondary fuel available from each of a secondremainder of the secondary fuel supplies 112 associated with a secondremainder of the GTEs 106. For example, the controller 116 may determinewhether, after switching the first GTE 106 to operation using secondaryfuel from its associated secondary fuel supply 112, any of the remainingGTEs 106 are receiving insufficient primary fuel to operate at thedesired output. In some instances, switching the first GTE 106 to thesecondary fuel may result in the remaining GTEs 106 receiving sufficientfuel to operate at the desired output. However, if one or more of theremaining GTEs 106 are not receiving sufficient primary fuel to operateat the desired output (e.g., the fuel pressure drops below the low-endset point), the controller 116 may be configured to determine, based atleast in part on the primary signals received from the primary sensors110 associated with the remaining GTEs 106, that one or more of theremaining GTEs 106 is receiving insufficient primary fuel from theprimary fuel source 108 to operate at the desired output.

In some such examples, the controller 116 may be configured to cause aprimary valve 506 of the plurality of primary valves 506 to inhibit flowcommunication between the primary fuel source 108 and the second of theplurality of GTEs 106. For example, the controller 116 may communicatewith one or more primary valves 506 associated with the second GTE 106and cause the one or more primary valves 506 to close, therebyinhibiting or shutting-off flow communication between the primary fuelsource 108 and the second GTE 106. In some examples, this may beperformed gradually.

The controller 116 may also be configured to cause supply of secondaryfuel from the second secondary fuel supply 112 to the second GTE 106.For example, the controller 116 may communicate with the pump 508configured to pump the secondary fuel from a secondary fuel supply 112associated with the second GTE 106 and cause the pump 508 to operate byactivating the pump 508. In some examples, the controller 116 may alsocommunicate with a secondary valve 510 configured to control flowcommunication between the secondary fuel supply 112 and the second GTE106, and cause the secondary valve 510 to open, thereby permittingsecondary fuel to be supplied to the second GTE 106. This may beperformed gradually. In some examples, this may be performed prior to,concurrently, substantially simultaneously, and/or followingshutting-off flow of the primary fuel to the second GTE 106.

In some examples, this process may be repeated, for example, until thecontroller 116 determines that the primary fuel source 108 is providingsufficient fuel to operate the remaining GTEs 106 still operating usingthe primary fuel at the desired output (e.g., at full capacity). In someexamples, it may be desirable to operate as many of the GTEs 106 aspossible using the primary fuel, and thus, the controller 116 may beconfigured to individually and sequentially switch the GTEs 106 fromoperation using primary fuel to operation using secondary fuel, untilthe primary fuel source 108 is capable of supplying a sufficient amountof primary fuel to the GTEs 106 to operate at the respective desiredoutput levels, with the remainder of the GTEs 106 operating using thesecondary fuel supplied by their respective secondary fuel supplies 112.By switching GTEs 106 having the greatest amount of secondary fuelavailable in their respective secondary fuel supplies 112 to operateusing secondary fuel, the duration of uninterrupted operation of theplurality of GTEs 106 may be increased and/or maximized.

In some examples, the controller 116 may be configured to continue tomonitor operation of the GTEs 106, for example, at the original datasampling rate and/or at the increased data sampling rate, and determinewhen the primary fuel source 108 has sufficient capacity to operate theremainder of the plurality of GTEs 106 at the desired output, wait aperiod of time (e.g., five minutes, ten minutes, or fifteen or moreminutes) after the determination, and determine whether (1) the primaryfuel source 108 continues to supply a sufficient amount of the primaryfuel to operate the remainder of the plurality of GTEs 106 at thedesired output, or (2) the primary fuel source 106 has insufficientcapacity to operate the remainder of the plurality of GTEs 106 at thedesired output. In some examples, the controller 116 may continue toreceive the primary signals generated by the primary sensors 110 andmake these determinations.

If the controller 116 determines that the primary fuel source 108continues to supply a sufficient amount of the primary fuel to operatethe remainder of the plurality of GTEs 106 at the desired output thecontroller 116 may also be configured to cease supply of secondary fuelfrom the first secondary fuel supply 112 to the first GTE 106. In someexamples, the controller 116 may check to determine whether the primaryfuel source 108 has increased its output to return to operating thefirst GTE 106 using primary fuel from the primary fuel source 108. Ifso, the controller 116 may cause the primary valve 506 of the pluralityof primary valves 506 to allow flow communication between the primaryfuel source 108 and the first GTE 108, for example, such that the firstGTE 106 is returned to operation using primary fuel supplied by theprimary fuel source 108. In some examples, this process may be repeatedfor each GTE 106 that has been switched to operation using secondaryfuel to see if one or more of such GTEs 106 may be returned to operationusing primary fuel.

In some examples, it the controller 116 determines that the primary fuelsource 108 has insufficient capacity to operate the remainder of theplurality of GTEs 106 at the desired output, the controller 116 may beconfigured to further determine, based at least in part on the secondarysignals from the secondary sensors 114, that the amount of secondaryfuel available from a second secondary fuel supply 112 associated with asecond of the plurality of GTEs 106 is greater than an amount ofsecondary fuel available from each of a second remainder of thesecondary fuel supplies 112 associated with a second remainder of GTEs106. For example, the controller 116 may determine whether, afterswitching the first GTE 106 to operation using secondary fuel from itsassociated secondary fuel supply 112, any of the remaining GTEs 106 arereceiving insufficient primary fuel. In some instances, switching thefirst GTE 106 to the secondary fuel may result in the remaining GTEs 106receiving sufficient fuel to operate at the desired output. However, ifone or more of the remaining GTEs 106 are not receiving sufficientprimary fuel to operate at the desired output (e.g., the fuel pressuredrops below a low-end set point), the controller 116 may be configuredto determine, based at least in part on the primary signals receivedfrom the primary sensors 110 associated with the remaining GTEs 106,that one or more of the remaining GTEs 106 is receiving insufficientprimary fuel from the primary fuel source 108 to operate at the desiredoutput.

In some examples, if the controller 116 determines that the primary fuelsource 108 has insufficient capacity to operate the remainder of theplurality of GTEs 106 at the desired output, the controller 116 may beconfigured to cause a primary valve 506 associated with the second GTE106 to inhibit (e.g., shut-off) flow communication between the primaryfuel source 108 and a second GTE of the plurality of GTEs 106, forexample, in a manner at least similar to that described above.

The controller 116 may also be configured to cause supply of secondaryfuel from the second secondary fuel supply 112 to the second GTE 106,for example, in a manner at least similar to that described above. Insome examples, the controller 116 may be configured to make a newdetermination about whether the primary fuel source 108 is providing asufficient amount of fuel to all the GTEs 106 operating using primaryfuel.

In this example manner, the controller 116 may determine that one ormore of the GTEs 106 is not receiving a sufficient amount of primaryfuel from the primary fuel source 108 to operate at the desired output.The controller 116 may also identify a GTE 106 from the plurality ofGTEs 106 that has the greatest amount of secondary fuel available in itsrespective secondary fuel supply 112 to operate its associated GTE 106,and switch operation of the identified GTE 106 from primary fuel to thesecondary fuel supplied by its associated secondary fuel supply 112.Thereafter, the controller 116 may determine whether, following theswitch and optionally waiting a period of time, any of the remainingGTEs 106 have insufficient primary fuel to operate at the desiredoutput. If so, the controller 116 may identify an additional GTE 106,from among the remaining GTEs 106 operating on primary fuel, having thegreatest amount of secondary fuel available in its respective secondaryfuel supply 112, and switch operation of the identified additional GTE106 from primary fuel to the secondary fuel. This may continue until allthe remaining GTEs 106 that have not been switched to operation usingsecondary fuel are operable at the desired output using the primaryfuel. Once all the remaining GTEs 106 are operable at the desired outputusing the primary fuel, the controller 116 may individually and/orsequentially restore operation of the GTEs 106 from operation usingsecondary fuel to operation using primary fuel, so long as the primaryfuel source 108 supplies sufficient primary fuel to operate the restoredGTEs 106. For example, after each of the GTEs 106 are restored tooperation using primary fuel, the controller 116 may determine whetherthe GTEs 106 operating using primary fuel are all receiving a sufficientamount of primary fuel to operate at the desired output. If so, thecontroller 116 may restore an additional GTE 106 back to operation usingprimary fuel and determine again whether the GTEs 106 operating usingprimary fuel are all receiving a sufficient amount of primary fuel tooperate at the desired output. In some examples, so long as the GTEs 106operating using primary fuel continue receiving a sufficient amount ofprimary fuel to operate at the desired output, the controller 116 maycontinue to restore GTEs 106 back to operation using the primary fuel,or until all the GTEs 106 are operating using the primary fuel. If, onthe other hand, the controller 116 determines that less than all theGTEs 106 are operable using the primary fuel, it may cause operation ofas few of the GTEs 106 as possible using the secondary fuel, forexample, until the supply of primary fuel is sufficient to operate allthe GTEs 106 using the primary fuel.

In yet another example, the controller 116 may be configured todetermine that one or more of the GTEs 106 is receiving insufficientprimary fuel from the primary fuel source 108 and switch operation of atleast some (e.g., all) of the GTEs 106 to operation using secondary fuelsupplied by the respective secondary fuel sources 114, and thereafter,restore operation of the GTEs 106 to primary fuel, for example, asoutlined below, and/or manage operation of the GTEs 106 using acombination of primary fuel and secondary fuel. In some examples, thecontroller 116 may be configured to perform this semi- orfully-autonomously. In some examples, one or more of the plurality ofGTEs 106 may be coupled to a pump 104 of a hydraulic fracturing unit102, and a plurality of the hydraulic fracturing units 102 may beincorporated into a hydraulic fracturing system 100 for fracturing asubterranean formation.

For example, the controller 116 may be configured to determine, based atleast in part on one or more primary signals, that the primary fuelsource 108 does not have an ability to supply an amount of primary fuelsufficient to operate the all of the plurality of GTEs 106 at thedesired output (e.g., full capacity). For example, the controller 116may receive the one or more primary signals and determine whether thefuel pressure has fallen below a predetermined low-end set point, whichmay correspond to a previously determined supply pressure consistentwith an inability of one or more of the GTEs 106 to operate at a desiredoutput using the primary fuel from the primary fuel source.

In some such examples, the controller 116 may be configured to cause oneor more primary valves 506 and/or 506′ (see FIG. 5 ) configured tocontrol flow communication between the primary fuel source 108 and theplurality of GTEs 106 to inhibit or shut-off flow communication betweenthe primary fuel source 108 and the plurality of GTEs 106 (e.g., inhibitor shut-off flow of primary fuel to all the GTEs 106). For example, aplurality of primary valves 506 may be provided and configured tocontrol flow communication between the primary fuel source 108 and eachof respective ones of the plurality of GTEs 106. The controller 116 maycommunicate with one or more of the primary valves 506 and cause the oneor more primary valves 506 to close, thereby inhibiting or shutting-offflow communication between the primary fuel source 108 and each of theGTEs 106. In some examples, this may be performed gradually as describedpreviously herein.

The controller 116, in some examples, may also be configured to causesupply of secondary fuel from a plurality of secondary fuel supplies 112to each of the plurality of GTEs 106, where each of the plurality ofsecondary fuel supplies 112 is associated with one of the plurality ofGTEs 106. For example, the controller 116 may communicate with one ormore pumps 508 (see FIG. 5 ) configured to pump secondary fuel from eachof a plurality of secondary fuel supplies 112, each associated with oneof the plurality of GTEs 106 and cause the pump(s) 508 to operate tosupply secondary fuel to each of the GTEs 106. In some examples, thecontroller 116 may also communicate with a plurality of secondary valves510 (see FIG. 5 ) configured to control flow communication between therespective secondary fuel supplies 112 and the respective GTEs 106, andcause the secondary valves 510 to open, thereby permitting secondaryfuel to be supplied to each of the GTEs 106 from the respectivesecondary fuel supplies 112. This may be performed gradually asdescribed previously herein. In some examples, this may be performedprior to, concurrently, substantially simultaneously, and/or followingshutting-off flow of the primary fuel to the GTEs 106. Thereafter, insome examples, at least for a period of time (e.g., five minutes, tenminutes, or fifteen or more minutes), the controller 116 cause operationof the plurality of GTEs 106 at the desired output (e.g., full capacity)using the secondary fuel.

In some examples, the controller 116 may be further configured to causeflow communication between the primary fuel source 108 and one or moreof the plurality of GTEs 106. For example, the controller 116 may beconfigured to individually and/or sequentially cause the GTEs 106 toswitch from operation using the secondary fuel to operation using theprimary fuel from the primary fuel source 108. This may includecommunicating with the pump 508 and in some examples, the secondaryvalve 510, associated with one of the GTEs 106 to cease supply of thesecondary fuel to the GTE 106. This may also include opening the primaryvalve 506 associated with the GTE 106 to restore flow communicationbetween the primary fuel source 108 and the GTE 106, and operating theGTE 106 using the primary fuel.

The controller 116 in some examples may also be configured to determine,based at least in part on one or more of the primary signals, whetherthe primary fuel source 108 has an ability to supply an amount ofprimary fuel sufficient to operate the GTE 106 restored to operationusing the primary fuel at the desired output. For example, afterrestoration of supply of primary fuel to the GTE 106, the controller 116may be configured to receive one or more primary signals from a primarysensor 110 associated with the GTE 106 and, based at least in part onthe one or more primary signals, determine whether the primary fuelsource 108 is able to supply a sufficient amount of fuel (e.g., the fuelpressure is above a low-end set point) to operate the GTE 106 at thedesired output.

The controller 116 may be configured to thereafter, based at least inpart on determining that the primary fuel source 108 has an ability tosupply an amount of primary fuel sufficient to operate the one GTE 106at the desired output, cause flow communication between the primary fuelsource 108 and one or more additional GTEs 106 of the plurality of GTEs106. For example, the controller 116 may be configured to individuallyand/or sequentially restore supply of the primary fuel to additionalGTEs 106 of the plurality of GTEs 106, for example, in a manner at leastsimilar to described above.

The controller 116 may also be configured to, based at least in part onone or more primary signals, determine whether the primary fuel source108 has an ability to supply an amount of primary fuel sufficient tooperate the GTEs 106 that have been restored to operation using theprimary fuel source 108 at the desired output. For example, afterrestoring supply of the primary fuel to each of the additional GTEs 106,the controller 116 may be configured to determine whether the primaryfuel source 108 has an ability to supply an amount of primary fuelsufficient to operate each of the GTEs 106 to which operation using theprimary fuel has been restored, for example, in a manner at leastsimilar to described above. Thus, in some examples, the controller 116may be configured to return operation of GTEs 106 using secondary fuelto operation using primary fuel until the controller 116 determines thatthe primary fuel source 108 is unable to supply a sufficient amount ofprimary fuel to operate all the restored GTEs 106 at the desired output.

For example, the controller 116 be configured to cause sequentialrestoration of flow communication between the primary fuel source 108and each of the plurality of GTEs 106, until the controller 116determines, based at least in part on one or more primary signals fromthe primary sensors 110, that the primary fuel source 108 lacks theability to supply an amount of primary fuel sufficient to operate at thedesired output (e.g., at substantially full capacity) a portion (e.g.,all) of the plurality of GTEs 106 to which flow communication with theprimary fuel source has been restored. For example, the controller 116may receive a plurality of primary signals from the primary sensorsassociated with each of the GTEs 106 to which operation using theprimary fuel has been restored and determine whether the primary fuelsource is able to supply a sufficient amount of the primary fuel to therestored GTEs 106 to operate the restored GTEs 106 at the desiredoutput. In some examples, this may be repeated until either (1) thecontroller 116 determines that the primary fuel source 108 lacks theability to supply an amount of primary fuel sufficient to operate therestored GTEs 106 at the desired output, or (2) all the GTEs 106 havebeen restored to operation using primary fuel from the primary fuelsource 108. If (1), the controller 116 may continue to operate at leasta subset of the GTEs 106 still operating using secondary fuel from theone or more corresponding secondary fuel supplies 112, for example, asdescribed in more detail below. If (2), the controller 116 may beconfigured to determine whether the primary fuel source 108 is able tosupply an amount of primary fuel sufficient to operate all the pluralityof GTEs 106 at the desired output.

In some examples, the controller 116 may be configured to manage flowcommunication between the primary fuel source 108 and each of theplurality of GTEs 106, for example, such that a first portion of theplurality of GTEs 106 are supplied with primary fuel from the primaryfuel source 108 and a second portion of the plurality of GTEs 106 aresupplied with secondary fuel from a portion of the plurality ofsecondary fuel supplies 112 associated with each of the second portionof the GTEs 106, such that the plurality of GTEs 106 are operated at thedesired output. For example, the controller 116 may be configured torestore operation of a portion of the GTEs 106 using the primary fuel,while maintaining operation of the remainder of the GTEs 106 using thesecondary fuel from the respective secondary fuel supplies 112.

In some examples, the controller 116 may be configured to periodicallycause: (1) a first subset of the first portion of the plurality of GTEs106 to switch from using primary fuel from the primary fuel source 108to each using secondary fuel from the secondary fuel supply 112associated with each of the plurality of the first subset of GTEs 106.The controller 116 may be configured to further cause a second subset ofthe second portion of the plurality of GTEs 106 to switch from usingsecondary fuel from the secondary fuel supply 112 associated with eachof the plurality of the second subset of GTEs 106 to operation usingprimary fuel from the primary fuel source 108. In some examples, thenumber of the plurality of GTEs 106 in the first subset may equal thenumber of the plurality of the GTEs 106 in the second subset. In someexamples, the first portion of the plurality of GTEs 106 and the secondportion of the plurality of GTEs 106 may include all of the plurality ofGTEs 106.

The controller 116, in some examples, may be configured to furtherinclude waiting a period of time, such as, for example, five minutes,ten minutes, fifteen minutes, or more. For example, the controller 116may initiate a clock to wait a period of time before taking furtheraction. Thereafter, the controller 116 may be configured to cause atleast some (e.g., all) of the first subset of GTEs 106 to switch fromoperation using secondary fuel to operation using primary fuel, andcause an equal number of the second subset of GTEs 106 to switch fromoperation using primary fuel to operation using secondary fuel, forexample, as previously described herein.

Thereafter, the controller 116 may be configured to further causeanother subset of the first portion of the plurality of GTEs 106 toswitch operation using primary fuel to operation using secondary fuel.The controller 116 may cause this action, for example, as previouslydescribed herein. The controller 116 may also be configured to causeanother subset of the second portion of the plurality of GTEs 106 toswitch from operation using secondary fuel to operation using primaryfuel. Similar to above, the controller 116 may cause waiting a period oftime, such as, for example, five minutes, ten minutes, fifteen minutes,or more, by initiating a clock to wait the period of time before takingfurther action.

In some examples, the controller 116 may be configured to cause repeatof the above-noted operations, for example, such that different subsetsof the GTEs 106 alternate between operation using primary fuel andoperation using secondary fuel. For example, once the number (e.g., themaximum number) of the plurality of GTEs 106 that may be supplied withthe primary fuel for operation at the desired output has been determinedand/or the number of GTEs 106 that must be operated using the secondaryfuel while all the GTEs 106 are operated at the desired output, the typeof fuel (e.g., the primary fuel or the secondary fuel) used by the GTEs106 may be periodically switched, for example, according to a routinethat switches some GTEs 106 operating using the primary fuel tooperating using the secondary fuel, and switching some GTEs 106operating using the secondary fuel to operating using the primary fuel.In some examples, the number of GTEs 106 being switched betweenoperation using the different types of fuel may be equal. For example,if two GTEs 106 operating using primary fuel are switched to operationusing secondary fuel, two GTEs 106 operating using secondary fuel may beswitched to operation using primary fuel. In some examples, suchswitching may occur following a predetermined amount of time (e.g., fiveminutes, ten minutes, or fifteen or more minutes). In some examples,such switching may occur such that most, or all, of the GTEs 106 areswitched between operation using the two types of fuel, for example,according to a repeating schedule. In some examples, this may result inless wear on the GTEs 106, for example, if the GTEs operate moreefficiently, with higher output, and/or with less wear, operating usingthe primary fuel relative to operation using the secondary fuel.

In some examples, the controller 116 may be configured to manage flowcommunication between the primary fuel source 108 and each of theplurality of GTEs 106, until the controller 116 determines, based atleast in part on one or more primary signals, that the primary fuelsource 108 is supplying sufficient primary fuel to operate all of theplurality of GTEs 106 at the desired output. For example, the controller116 may receive the primary signals and determine that it is possible tooperate all of the GTEs 106 using the primary fuel, and at such time,the controller 116 may cause all the GTEs 106 to operate using theprimary fuel. For example, a cause preventing the primary fuel source108 from supplying a sufficient amount of primary fuel to operate allthe GTEs 106 using the primary fuel may be identified and mitigatedand/or eliminated. For example, a source of the primary fuel may restoresufficient primary fuel and/or pressure to the system for the system tooperate solely using primary fuel, and/or a compromised fuel filter 504preventing sufficient fuel pressure and/or flow may be cleaned orreplaced, thus correcting a problem preventing a sufficient amount ofprimary fuel from being supplied to the GTEs 106 to operate them allsimultaneously at the desired output.

FIGS. 6, 7A, 7B, 8A, and 8B are a block diagrams of example methods forcontrolling supply of fuel to a plurality of GTEs according toembodiments of the disclosure illustrated as a collection of blocks in alogical flow graph, which represent a sequence of operations that may beimplemented in hardware, software, or a combination thereof. In thecontext of software, the blocks represent computer-executableinstructions stored on one or more computer-readable storage media that,when executed by one or more processors, perform the recited operations.Generally, computer-executable instructions include routines, programs,objects, components, data structures, and the like that performparticular functions or implement particular data types. The order inwhich the operations are described is not intended to be construed as alimitation, and any number of the described blocks can be combined inany order and/or in parallel to implement the methods.

FIG. 6 is a flow diagram of an example method 600 for controlling fuelsupply to a plurality or fleet of GTEs associated with pumps in ahydraulic fracturing system according to embodiments of the disclosure.In some examples, the method 600 may be performed semi- orfully-autonomously. The method 600 may be utilized in association withvarious systems, such as, for example, the systems 100, 200, 300, 400,and/or 500 illustrated in FIGS. 1, 2, 3, 4 , and/or 5.

The example method 600, at 602, may include receiving a signalindicating that supply pressure of primary fuel supplied to one or moreGTEs connected to a pump of a plurality of pumps falls below a setpoint. For example, a primary sensor may generate one or more signalsindicative of the supply pressure, and a controller may receive the oneor more signals and determine whether the supply pressure has fallenbelow a predetermined set point, which may correspond to a previouslydetermined supply pressure consistent with an inability of one or moreof the GTEs to operate at a desired output (e.g., at full capacity)using the primary fuel.

The example method 600, at 604, may further include initiating a timerand increasing a data sampling rate associated with the plurality GTEs,for example, based at least in part on the signal. For example, if undernormal operating conditions the controller samples data at a firstsampling rate, the controller may start a timer and sample the data at afaster sampling rate, for example, as described previously herein.

The example method 600, at 606, may also include, when the supplypressure of primary fuel to the one or more GTEs remains below the setpoint when the timer reaches a predetermined end time, identifying a GTEof the plurality of GTEs having a greatest amount of a secondary fuelavailable. For example, a secondary sensor associated with each of theGTEs may be configured to generate one or more signals indicative of anamount of secondary fuel available to each of the GTEs from a secondaryfuel supply associated with each of the GTEs. The controller may receivethe signals and identify the GTE corresponding to the secondary fuelsupply having the greatest amount of secondary fuel from among all ofthe secondary fuel supplies.

At 608, the example method 600 may further include causing supply of thesecondary fuel to the identified GTE in place of at least some of theprimary fuel (e.g., all of the primary fuel) supplied to the identifiedGTE. For example, the controller may communicate with one or moreprimary valves associated with the identified GTE and cause the one ormore primary valves to close, thereby shutting-off flow communicationbetween the primary fuel source and the identified GTE. In someexamples, this may be performed gradually. The controller may also causesecondary fuel from the secondary fuel supply associated with theidentified GTE to be supplied to the identified GTE. For example, thecontroller may communicate with a pump configured to pump the secondaryfuel from the secondary fuel supply to the identified GTE and cause thepump to operate. In some examples, the controller may also communicatewith a secondary valve configured to control flow communication betweenthe secondary fuel supply and the identified GTE, and cause thesecondary valve to open, thereby permitting secondary fuel to besupplied to the identified GTE. This may be performed gradually. In someexamples, this may be performed prior to, concurrently, substantiallysimultaneously, and/or following shutting-off flow of the primary fuelto the identified GTE.

In some examples of the method 600, 602 through 608 may be repeated forone or more of the remaining GTEs of the plurality or fleet of GTEsassociated with the pumps of the hydraulic fracturing system, forexample, when the controller determines that the primary fuel supply isunable to supply an amount of primary fuel to a GTE to operate the GTEat the desired output.

At 610, the example method 600 may also include receiving a secondsignal indicating that supply pressure of primary fuel to one or moreGTEs rises above a second set point. For example, one or more of theprimary sensors may receive a signal indicative that the primary fuelsource is supplying sufficient fuel pressure to operate the GTEs usingthe primary fuel.

At 612, the example method 600 may further include, based at least inpart on the indication at 610, initiating a second timer.

At 614, the example method 600 may further include transferringoperation of the one or more GTEs to primary fuel operation, forexample, if the supply pressure of primary fuel to the one or more GTEsremains above the second set point when the second timer reaches asecond predetermined end time. For example, if the controller receivesthe one or more signals from the primary sensor associated with the oneor more GTEs, and the one or more signals indicates that supply pressureis greater than the second set point after monitoring the supplypressure for the predetermined period of time, it indicates that theprimary fuel source is suppling an amount of primary fuel sufficient tooperate the one or more GTEs, and thus, the controller may cause the oneor more GTEs to return to operation using primary fuel from the primaryfuel source. This may include opening the primary valve providing flowcommunication between the primary fuel source and the one or more GTEs,and closing a secondary valve between the secondary fuel supply and theone or more GTEs and/or ceasing operation of a pump configured to supplythe secondary fuel to the one or more GTEs.

At 616, the example method may further include decreasing the datasampling rate for the one or more GTEs operating using primary fuel. Forexample, the controller may return the sampling to the sampling rateprior to 604 above.

FIGS. 7A and 7B are a flow diagram of an example method 700 forsupplying fuel to a plurality or fleet of GTEs according to embodimentsof the disclosure. In some examples, the method 700 may be performedsemi- or fully-autonomously. The method 700 may be utilized inassociation with various systems, such as, for example, the systems 100,200, 300, 400, and/or 500 illustrated in FIGS. 1, 2, 3, 4 , and/or 5.For example, one or more of the plurality of GTEs may be coupled to apump of a hydraulic fracturing unit, and a plurality of the hydraulicfracturing units may be incorporated into a hydraulic fracturing systemfor fracturing a subterranean formation.

At 702, the example method 700 may include determining, based at leastin part on a primary signal, that a primary fuel source is supplying aninsufficient amount of primary fuel to operate one or more of theplurality of GTEs at the first output, such as a desired outputassociated with operation of the GTE (e.g., full capacity output). Forexample, a primary sensor associated with one or more of the pluralityof GTEs (e.g., a primary sensor associated with each of the GTEs) may beconfigured to generate a primary signal indicative of an ability of aprimary fuel source to supply an amount of primary fuel sufficient tooperate the plurality of GTEs (e.g., each of the GTEs) at a first outputmay generate one or more signals indicative of a fuel pressure, and acontroller may receive the one or more signals and determine whether thefuel pressure has fallen below a predetermined set point, which maycorrespond to a previously determined supply pressure consistent with aninability of one or more of the GTEs to operate at a desired output(e.g., full capacity) using the primary fuel from the primary fuelsource.

At 704, the example method 700 may further include determining, based atleast in part on secondary signals indicative of an amount of secondaryfuel available from a secondary fuel supply associated with each of theplurality of GTEs, that the amount of secondary fuel available from afirst secondary fuel supply associated with a first of the plurality ofGTEs is greater than an amount of secondary fuel available from each ofa remainder of the secondary fuel supplies associated with a remainderof the plurality of GTEs. For example, a plurality of secondary sensors,each of which is associated with one of the plurality of GTEs, may beconfigured to generate a secondary signal indicative of an amount ofsecondary fuel available from a secondary fuel supply associated witheach of the plurality of GTEs. The secondary sensors may generate theone or more secondary signals, and the controller may be configured toreceive the secondary signals and determine or identify, based at leastin part on the secondary signals, that a first one of the secondary fuelsupplies associated with a corresponding first one of the plurality ofGTEs, has a greater amount of secondary fuel available than theremaining secondary fuel supplies associated with each of the otherremaining GTEs.

The example method 700, at 706, may further include causing a primaryvalve of the plurality of primary valves to inhibit flow communicationbetween the primary fuel source and the first of the plurality of GTEs.For example, each of a plurality of primary valves may be provided andconfigured to control flow communication between the primary fuel sourceand one of the plurality of GTEs. The controller may communicate withone or more primary valves associated with the first GTE and cause theone or more primary valves to close, thereby inhibiting or shutting-offflow communication between the primary fuel source and the first GTE. Insome examples, this may be performed gradually.

At 708, the example method 700 may further include causing supply ofsecondary fuel from a first secondary fuel supply associated with thefirst GTE to the first GTE of the plurality of GTEs. For example, thecontroller may communicate with a pump configured to pump the secondaryfuel from a secondary fuel supply associated with the first GTE andcause the pump to operate. In some examples, the controller may alsocommunicate with a secondary valve configured to control flowcommunication between the secondary fuel supply and the first GTE, andcause the secondary valve to open, thereby permitting secondary fuel tobe supplied to the first GTE. This may be performed gradually. In someexamples, this may be performed prior to, concurrently, substantiallysimultaneously, and/or following shutting-off flow of the primary fuelto the first GTE.

The example method 700, at 710, may further include determining, aftercausing the primary valve to inhibit flow communication between theprimary fuel source and the first of the GTEs, based at least in part onthe primary signal, whether the primary fuel source is supplying asufficient amount of the primary fuel to operate the remainder of theplurality of GTEs at the first output (e.g., at full capacity of each ofthe GTEs). In some examples, this may include the controller receivingprimary signals from one or more of the primary sensors (e.g., all ofthe primary sensors associated with each of the remaining GTEs) anddetermining whether any of the remaining GTEs are receiving insufficientprimary fuel to operate at the desired output. In some examples, one ormore of such primary signals may be indicative of an insufficient fuelpressure.

At 712, the example method 700 may include, when it has been determinedat 710 that the primary fuel source is not supplying a sufficient amountof the primary fuel to operate the remainder of the plurality of GTEs atthe first output, determining, based at least in part on the secondarysignals, that the amount of secondary fuel available from a secondsecondary fuel supply associated with a second of the plurality of GTEsis greater than an amount of secondary fuel available from each of asecond remainder of the secondary fuel supplies associated with a secondremainder of GTEs. For example, the controller may determine whether,after switching the first GTE to operation using secondary fuel from itsassociated secondary fuel supply, any of the remaining GTEs arereceiving insufficient primary fuel. In some instances, switching thefirst GTE to the secondary fuel may result in the remaining GTEsreceiving sufficient fuel to operate at the desired output. However, ifone or more of the remaining GTEs are not receiving sufficient primaryfuel to operate at the desired output (e.g., the fuel pressure dropsbelow a set point), the controller may be configured to determine, basedat least in part on the primary signals received from the primarysensors associated with the remaining GTEs, that one or more of theremaining GTEs is receiving insufficient primary fuel from the primaryfuel source to operate at the desired output.

At 714, the example method 700 may include causing a primary valve ofthe plurality of primary valves to inhibit flow communication betweenthe primary fuel source and the second of the plurality of GTEs. Forexample, the controller may communicate with one or more primary valvesassociated with the second GTE and cause the one or more primary valvesto close, thereby inhibiting or shutting-off flow communication betweenthe primary fuel source and the second GTE. In some examples, this maybe performed gradually.

At 716, the example method may include causing supply of secondary fuelfrom the second secondary fuel supply to the second GTE of the pluralityof GTEs. For example, the controller may communicate with a pumpconfigured to pump the secondary fuel from a secondary fuel supplyassociated with the second GTE and cause the pump to operate. In someexamples, the controller may also communicate with a secondary valveconfigured to control flow communication between the secondary fuelsupply and the second GTE, and cause the secondary valve to open,thereby permitting secondary fuel to be supplied to the second GTE. Thismay be performed gradually. In some examples, this may be performedprior to, concurrently, substantially simultaneously, and/or followingshutting-off flow of the primary fuel to the second GTE.

In some examples of the method 700, one or more of 710 through 716 maybe repeated, for example, until it has been determined that the primaryfuel source is providing sufficient fuel to operate the remaining GTEsstill operating using the primary fuel at the desired output (e.g., atfull capacity). In some examples, it may be desirable to operate as manyof the GTEs of the plurality of GTEs as possible using the primary fuel,and thus, the method may include individually and sequentially switchingthe GTEs from operation using primary fuel to operation using secondaryfuel, until the primary fuel source is capable of supplying a sufficientamount of primary fuel to the GTEs still operating using the primaryfuel to operate at the respective desired output levels, with the restof the GTEs operating using the secondary fuel supplied by theirrespective secondary fuel supplies. By switching GTEs having thegreatest amount of secondary fuel available in their respectivesecondary fuel supplies to operate using secondary fuel, the duration ofuninterrupted operation of the plurality of GTEs may be increased and/ormaximized.

As shown in FIG. 7B, the example method 700, at 718, may furtherinclude, when it has been determined at 710 the primary fuel source hassufficient capacity to operate the remainder of the plurality of gasturbine engines at the first output, waiting a period of time anddetermining whether (1) the primary fuel source continues to supply asufficient amount of the primary fuel to operate the remainder of theplurality of GTEs at the first output, or (2) the primary fuel sourcehas insufficient capacity to operate the remainder of the plurality ofGTEs at the first output. In some examples, the controller may continueto receive the primary signals from the primary sensors and make thisdetermination.

The example method, at 720, may further include, if at 718 it isdetermined that the primary fuel source continues to supply a sufficientamount of the primary fuel to operate the remainder of the plurality ofGTEs at the first output, ceasing supply of secondary fuel from thefirst secondary fuel supply to the first GTE of the plurality of GTEs.In some examples, the controller may determine whether the primary fuelhas increased its output to return to operating the first GTE usingprimary fuel from the primary fuel source. If so, the controller maycause the primary valve of the plurality of primary valves to allow flowcommunication between the primary fuel source and the first GTE, forexample, such that the first GTE is returned to operation using primaryfuel supplied by the primary fuel source. In some examples, the method700 may repeat 718 for each GTE that has been switched to operationusing secondary fuel to see if one or more of such GTEs may be returnedto operation using primary fuel.

The example method 700, at 722, may further include, if at 718 it isdetermined that the primary fuel source has insufficient capacity tooperate the remainder of the plurality of GTEs at the first output,determining, based at least in part on the secondary signals, that theamount of secondary fuel available from a second secondary fuel supplyassociated with a second of the plurality of GTEs is greater than anamount of secondary fuel available from each of a second remainder ofthe secondary fuel supplies associated with a second remainder of GTEs.For example, the controller may determine whether, after switching thefirst GTE to operation using secondary fuel from its associatedsecondary fuel supply, any of the remaining GTEs are receivinginsufficient primary fuel. In some instances, switching the first GTE tothe secondary fuel may result in the remaining GTEs receiving sufficientprimary fuel to operate at the desired output. However, if one or moreof the remaining GTEs are not receiving sufficient primary fuel tooperate at the desired output (e.g., the fuel pressure drops below a setpoint), the controller may be configured to determine, based at least inpart on the primary signals received from the primary sensors associatedwith the remaining GTEs, that one or more of the remaining GTEs isreceiving insufficient primary fuel from the primary fuel source tooperate at the desired output.

The example method 700, at 724, may further include, if at 718 it isdetermined that the primary fuel source has insufficient capacity tooperate the remainder of the plurality of GTEs at the first output,causing a primary valve associated with the second GTE to inhibit (e.g.,shut-off) flow communication between the primary fuel source and asecond GTE, for example, in a manner at least similar to 706 above.

The example method 700, at 726, may further include, causing supply ofsecondary fuel from the second secondary fuel supply to the second GTE,for example, in a manner at least similar to 708 above. In someexamples, following 726, the method 700 may return to 718 to make a newdetermination about whether the primary fuel source is providing asufficient amount of fuel to all the GTEs operating using primary fuel.

In this example manner, the method may include identifying that one ormore of the GTEs is not receiving a sufficient amount of primary fuelfrom the primary fuel source to operate at the desired output. Themethod further may include identifying a GTE from the plurality of GTEsthat has the greatest amount of secondary fuel available in itsrespective secondary fuel supply to operate its associated GTE, andswitch operation of the identified GTE from primary fuel to thesecondary fuel supplied by its associated secondary fuel supply.Thereafter, the method may include determining whether, following theswitch and optionally waiting a period of time, any of the remainingGTEs have insufficient primary fuel to operate at the desired output. Ifso, the method may include identifying a GTE, from among the remainingGTEs operating on primary fuel, having the greatest amount of secondaryfuel available in its respective secondary fuel supply, and switchingoperation of the identified GTE from primary fuel to the secondary fuel.This may continue until all the remaining GTEs still operating usingprimary fuel are operable at the desired output. Once all the remainingGTEs are operable at the desired output using the primary fuel, themethod may include individually and sequentially switching operation ofthe GTEs from operation using secondary fuel to operation using primaryfuel. After each of the GTEs are switched back to operation usingprimary fuel, the method may include determining whether the GTEsoperating using primary fuel are all receiving a sufficient amount ofprimary fuel to operate at the desired output. If so, the method mayinclude switching an additional GTE back to operation using primary fueland determining again whether the GTEs operating using primary fuel areall receiving a sufficient amount of primary fuel to operate at thedesired output. In some examples, so long as the GTEs operating usingprimary fuel continue receiving a sufficient amount of primary fuel tooperate at the desired output, the method may include continuing toswitch GTEs back to operation using the primary fuel, or until all theGTEs are operating using the primary fuel. If, on the other hand, themethod determines that less than all the GTEs are operable using theprimary fuel, the method may include operating as few of the GTEs aspossible using the secondary fuel, for example, until the supply ofprimary fuel is sufficient to operate all the GTEs using the primaryfuel.

FIGS. 8A and 8B are a flow diagram of another example method 800 forsupplying fuel to a plurality or fleet of GTEs according to embodimentsof the disclosure. In some examples, the method 800 may be performedsemi- or fully-autonomously. The method 800 may be utilized inassociation with various systems, such as, for example, the systems 100,200, 300, 400, and/or 500 illustrated in FIGS. 1, 2, 3, 4 , and/or 5.For example, one or more of the plurality of GTEs may be coupled to apump of a hydraulic fracturing unit, and a plurality of the hydraulicfracturing units may be incorporated into a hydraulic fracturing systemfor fracturing a subterranean formation.

At 802, the example method 800 may include determining, based at leastin part on one or more primary signals, that a primary fuel source doesnot have an ability to supply an amount of primary fuel sufficient tooperate the plurality of GTEs at the first output (e.g., a desiredoutput and/or at full capacity). For example, a primary sensorassociated with one or more of the plurality of GTEs (e.g., a primarysensor associated with each of the GTEs) may be configured to generate aprimary signal indicative of an ability of a primary fuel source tosupply an amount of primary fuel sufficient to operate the plurality ofGTEs (e.g., each of the GTEs) at a first output may generate one or moresignals indicative of a fuel pressure (e.g., upstream of each of theGTEs). A controller may receive the one or more signals and determinewhether the fuel pressure has fallen below a predetermined set point,which may correspond to a previously determined supply pressureconsistent with an inability of one or more of the GTEs to operate at adesired output using the primary fuel from the primary fuel source.

At 804, the example method 800 may also include causing one or moreprimary valves configured to control flow communication between theprimary fuel source and the plurality of GTEs to inhibit flowcommunication between the primary fuel source and the plurality of GTEs(e.g., inhibit or shut-off flow of primary fuel to all the GTEs). Forexample, a plurality of primary valves may be provided and configured tocontrol flow communication between the primary fuel source and each ofrespective ones of the plurality of GTEs. The controller may communicatewith one or more of the primary valves and cause the one or more primaryvalves to close, thereby inhibiting or shutting-off flow communicationbetween the primary fuel source and each of the GTEs. In some examples,this may be performed gradually.

The example method 800, at 806 may further include causing supply ofsecondary fuel from a plurality of secondary fuel supplies to each ofthe plurality of GTEs, where each of the plurality of secondary fuelsupplies is associated with one of the plurality of GTEs. For example,the controller may communicate with one or more pumps configured to pumpsecondary fuel from each of a plurality of secondary fuel supplies, eachassociated with one of the plurality of GTEs, and cause the pump(s) tooperate to supply secondary fuel to each of the GTEs. In some examples,the controller may also communicate with a plurality of secondary valvesconfigured to control flow communication between the respectivesecondary fuel supplies and the respective GTEs, and cause the secondaryvalves to open, thereby permitting secondary fuel to be supplied to eachof the GTEs from the respective secondary fuel supplies. This may beperformed gradually. In some examples, this may be performed prior to,concurrently, substantially simultaneously, and/or followingshutting-off flow of the primary fuel to the GTEs.

At 808, the example method 800 may also include causing operation of theplurality of GTEs at the first output (e.g., full capacity) using thesecondary fuel.

At 810, the example method 800 may further include causing flowcommunication between the primary fuel source and one or more of theplurality of GTEs. For example, the controller may be configured toindividually and/or sequentially cause the GTEs to switch from operationusing the secondary fuel to operation using the primary fuel from theprimary fuel source. This may include communicating with the pump and insome examples, the secondary valve, associated with one of the GTEs tocease supply of the secondary fuel to the GTE. This may also includeopening the primary valve associated with the GTE to restore flowcommunication between the primary fuel source and the GTE, and operatingthe GTE using the primary fuel.

The example method 800, at 812, may also include determining, based atleast in part on one or more of the primary signals, whether the primaryfuel source has an ability to supply an amount of primary fuelsufficient to operate the GTE restored to operation using the primaryfuel at the first output. For example, after restoration of the primaryfuel to the GTE, the controller may be configured to receive one or moreprimary signals generated by a primary sensor associated with the GTEand, based at least in part on the one or more primary signals,determine whether the primary fuel source is able to supply a sufficientamount of fuel (e.g., the fuel pressure is above a set point) to operatethe GTE at the first output.

At 814, the example method 800 may further include, based at least inpart on determining that the primary fuel source has an ability tosupply an amount of primary fuel sufficient to operate the one or moreGTEs at the first output, causing flow communication between the primaryfuel source and one or more additional GTEs of the plurality of GTEs.For example, the controller may be configured to individually and/orsequentially restore supply of the primary fuel to additional GTEs ofthe plurality of GTEs, for example, in a manner at least similar to 810.

The example method 800, at 816, may also include determining, based atleast in part on one or more primary signals, whether the primary fuelsource has an ability to supply an amount of primary fuel sufficient tooperate the GTEs that have been restored to operation using the primaryfuel source at the first output. For example, after restoring supply ofthe primary fuel to each of the additional GTEs, the controller may beconfigured to determine whether the primary fuel source has an abilityto supply an amount of primary fuel sufficient to operate each of theGTEs to which operation using the primary fuel has been restored, forexample, in a manner at least similar to 812. Thus, in some examples,the method may return to 814 until the controller determines that theprimary fuel source is unable to supply a sufficient amount of primaryfuel to operate all the restored GTEs at the first output.

For example, the method 800 may include, following 808, causingindividual and/or sequential restoration of flow communication betweenthe primary fuel source and each of the plurality of GTEs until it isdetermined, based at least in part on one or more primary signals, thatthe primary fuel source lacks an ability to supply an amount of primaryfuel sufficient to operate at the first output (e.g., at substantiallyfull capacity) the portion of the plurality of GTEs to which flowcommunication with the primary fuel source has been restored. Forexample, the controller may receive a plurality of primary signals fromthe primary sensors associated with each of the GTEs to which operationusing the primary fuel has been restored and determine whether theprimary fuel source is able to supply a sufficient amount of the primaryfuel to the restored GTEs to operate the restored GTEs at the desiredoutput. This may be repeated until either (1) the controller determinesthat the primary fuel source lacks an ability to supply an amount ofprimary fuel to operate the restored GTEs at the desired output, or (2)all the GTEs have been restored to operation using primary fuel from theprimary fuel source. If (1), the method 800 may include continuing tooperate at least a subset of the GTEs still operating using secondaryfuel from the one or more corresponding secondary fuel supplies, forexample, as described with respect to 818 through 832 below. This may becontrolled by the controller. If (2), the method 800 may return to 802to determine whether the primary fuel source is able to supply an amountof primary fuel sufficient to operate all the plurality of GTEs at thefirst or desired output. This may be performed by the controller, forexample, as described herein.

At 818, as shown in FIG. 8B, the example method 800 may include managingflow communication between the primary fuel source and each of theplurality of GTEs, for example, such that a first portion of theplurality of GTEs is supplied with primary fuel from the primary fuelsource and a second portion of the plurality of GTEs is supplied withsecondary fuel from a portion of the plurality of secondary fuelsupplies associated with each of the second portion of the GTEs, suchthat the plurality of GTEs are operated at the first output. Forexample, the controller may be configured to restore operation of aportion of the GTEs to using the primary fuel, while maintainingoperation of the remainder of the GTEs using the secondary fuel from therespective secondary fuel supplies.

At 820, the example method 800 may further include periodically causing:(1) a first subset of the first portion of the plurality of GTEs toswitch from using primary fuel from the primary fuel source to eachusing secondary fuel from the secondary fuel supply associated with eachof the plurality of the first subset. The controller may cause thisaction, for example, as previously described herein.

At 822, the example method 800 may further include causing a secondsubset of the second portion of the plurality of GTEs to switch fromusing secondary fuel from the secondary fuel supply associated with eachof the plurality of the second subset of GTEs to operation using primaryfuel from the primary fuel source. In some examples, the number of theplurality of GTEs in the first subset may equal the number of theplurality of the GTEs in the second subset. In some examples, the firstportion of the plurality of GTEs and the second portion of the pluralityof GTEs includes all of the plurality of GTEs. The controller may causethis action, for example, as previously described herein.

At 824, the example method 800 may further include waiting a period oftime, such as, for example, five minutes, ten minutes, fifteen minutes,or more. For example, the controller may initiate a clock to wait aperiod of time before taking further action.

At 826, the method 800 may include causing at least some (e.g., all) ofthe first subset of GTEs to switch from operation using secondary fuelto operation using primary fuel, and cause an equal number of the secondsubset of GTEs to switch from operation using primary fuel to operationusing secondary fuel. The controller may cause this action, for example,as previously described herein.

At 828, the example method 800 may further include causing anothersubset of the first portion of the plurality of GTEs to switch operationusing primary fuel to operation using secondary fuel. The controller maycause this action, for example, as previously described herein.

At 830, the example method may further include causing another subset ofthe second portion of the plurality of GTEs to switch from operationusing secondary fuel to operation using primary fuel. The controller maycause this action, for example, as previously described herein.

At 832, the example method may further include waiting a period of time,such as, for example, five minutes, ten minutes, fifteen minutes, ormore. For example, the controller may initiate a clock to wait a periodof time before taking further action.

In some examples, 826 through 832 may be repeated, such that differentsubsets of the GTEs alternate between operation using primary fuel andoperation using secondary fuel. For example, once the number (e.g., themaximum number) of the plurality of GTEs that may be supplied with theprimary fuel for operation at the desired output has been determinedand/or the number of GTEs that must be operated using the secondary fuelwhile all the GTEs are operated at the desired output, the type of fuel(e.g., the primary fuel or the secondary fuel) used by the GTEs may beswitched, for example, according to a routine that periodically switchessome GTEs operating using the primary fuel to operating using thesecondary fuel, and switching some GTEs operating using the secondaryfuel to operating using the primary fuel. In some examples, the numberof GTEs being switched between operation using the different types offuel may be equal. In other words, if two GTEs operating using primaryfuel are switched to operation using secondary fuel, two GTEs operatingusing secondary fuel may be switched to operation using primary fuel. Insome examples, such switching may occur following a predetermined amountof time (e.g., five minutes, ten minutes, fifteen minutes, twentyminutes, or thirty minutes). In some examples, such switching may occursuch that most, or all, of the GTEs are switched between operation usingthe two types of fuel, for example, according to a repeating schedule.In some examples, this may result in less wear on the GTEs, for example,if the GTEs operate more efficiently, with higher output, and/or withless wear, operating using the primary fuel relative to operating usingthe secondary fuel.

In some examples, method 800 may include managing flow communicationbetween the primary fuel source and each of the plurality of GTEs untilit has been determined, based at least in part on one or more primarysignals, that the primary fuel source is supplying sufficient primaryfuel to operate all of the plurality of GTEs at the first output. Forexample, the controller may receive the primary signals and determinethat it is possible to operate all of the GTEs using the primary fuel,and at such time, the controller may cause all the GTEs to operate usingthe primary fuel. For example, the cause preventing the primary fuelsource from supplying a sufficient amount of primary fuel to operate allthe GTEs using the primary fuel may be identified and mitigated and/oreliminated. For example, a source of the primary fuel may restoresufficient primary fuel and/or pressure to the system for the system tooperate solely using primary fuel, and/or a compromised fuel filterpreventing sufficient fuel pressure and/or flow may be cleaned orreplaced, thus correcting a problem preventing a sufficient amount ofprimary fuel from being supplied to the GTEs to operate them allsimultaneously at the desired output.

It should be appreciated that subject matter presented herein may beimplemented as a computer process, a computer-controlled apparatus, acomputing system, or an article of manufacture, such as acomputer-readable storage medium. While the subject matter describedherein is presented in the general context of program modules thatexecute on one or more computing devices, those skilled in the art willrecognize that other implementations may be performed in combinationwith other types of program modules. Generally, program modules includeroutines, programs, components, data structures, and other types ofstructures that perform particular tasks or implement particularabstract data types.

Those skilled in the art will also appreciate that aspects of thesubject matter described herein may be practiced on or in conjunctionwith other computer system configurations beyond those described herein,including multiprocessor systems, microprocessor-based or programmableconsumer electronics, minicomputers, mainframe computers, handheldcomputers, mobile telephone devices, tablet computing devices,special-purposed hardware devices, network appliances, and the like.

FIG. 9 illustrates an example controller 116 configured for implementingcertain systems and methods for supplying fuel to a plurality GTEs(e.g., dual- or bi-fuel GTEs configured to operate using two differenttypes of fuel) according to embodiments of the disclosure, for example,as described herein. The controller 116 may include one or moreprocessor(s) 900 configured to execute certain operational aspectsassociated with implementing certain systems and methods describedherein. The processor(s) 900 may communicate with a memory 902. Theprocessor(s) 900 may be implemented and operated using appropriatehardware, software, firmware, or combinations thereof. Software orfirmware implementations may include computer-executable ormachine-executable instructions written in any suitable programminglanguage to perform the various functions described. In some examples,instructions associated with a function block language may be stored inthe memory 902 and executed by the processor(s) 900.

The memory 902 may be used to store program instructions that areloadable and executable by the processor(s) 900, as well as to storedata generated during the execution of these programs. Depending on theconfiguration and type of the controller 116, the memory 902 may bevolatile (such as random access memory (RAM)) and/or non-volatile (suchas read-only memory (ROM), flash memory, etc.). In some examples, thememory devices may include additional removable storage 904 and/ornon-removable storage 906 including, but not limited to, magneticstorage, optical disks, and/or tape storage. The disk drives and theirassociated computer-readable media may provide non-volatile storage ofcomputer-readable instructions, data structures, program modules, andother data for the devices. In some implementations, the memory 902 mayinclude multiple different types of memory, such as static random accessmemory (SRAM), dynamic random access memory (DRAM), or ROM.

The memory 902, the removable storage 904, and the non-removable storage906 are all examples of computer-readable storage media. For example,computer-readable storage media may include volatile and non-volatile,removable and non-removable media implemented in any method ortechnology for storage of information such as computer-readableinstructions, data structures, program modules or other data. Additionaltypes of computer storage media that may be present may include, but arenot limited to, programmable random access memory (PRAM), SRAM, DRAM,RAM, ROM, electrically erasable programmable read-only memory (EEPROM),flash memory or other memory technology, compact disc read-only memory(CD-ROM), digital versatile discs (DVD) or other optical storage,magnetic cassettes, magnetic tapes, magnetic disk storage or othermagnetic storage devices, or any other medium which may be used to storethe desired information and which may be accessed by the devices.Combinations of any of the above should also be included within thescope of computer-readable media.

The controller 116 may also include one or more communicationconnection(s) 908 that may facilitate a control device (not shown) tocommunicate with devices or equipment capable of communicating with thecontroller 116. The controller 116 may also include a computer system(not shown). Connections may also be established via various datacommunication channels or ports, such as USB or COM ports to receivecables connecting the controller 116 to various other devices on anetwork. In some examples, the controller 116 may include Ethernetdrivers that enable the controller 116 to communicate with other deviceson the network. According to various examples, communication connections908 may be established via a wired and/or wireless connection on thenetwork.

The controller 116 may also include one or more input devices 910, suchas a keyboard, mouse, pen, voice input device, gesture input device,and/or touch input device. It may further include one or more outputdevices 912, such as a display, printer, and/or speakers. In someexamples, computer-readable communication media may includecomputer-readable instructions, program modules, or other datatransmitted within a data signal, such as a carrier wave or othertransmission. As used herein, however, computer-readable storage mediamay not include computer-readable communication media.

Turning to the contents of the memory 902, the memory 902 may include,but is not limited to, an operating system (OS) 914 and one or moreapplication programs or services for implementing the features andembodiments disclosed herein. Such applications or services may includea remote terminal unit 118 for executing certain systems and methods forcontrol of a fuel management system (e.g., semi- or full-autonomouscontrol of a fuel management system for bi- or dual-fuel GTEs). Theremote terminal unit 118 may reside in the memory 902 or may beindependent of the controller 116, for example, as depicted in FIG. 1 .In some examples, the remote terminal unit 118 may be implemented bysoftware that may be provided in configurable control block language andmay be stored in non-volatile memory. When executed by the processor(s)900, the remote terminal unit 118 may implement the variousfunctionalities and features associated with the controller 116described herein.

As desired, embodiments of the disclosure may include a controller 116with more or fewer components than are illustrated in FIG. 9 .Additionally, certain components of the example controller 116 shown inFIG. 9 may be combined in various embodiments of the disclosure. Thecontroller 116 of FIG. 9 is provided by way of example only.

References are made to block diagrams of systems, methods, apparatuses,and computer program products according to example embodiments. It willbe understood that at least some of the blocks of the block diagrams,and combinations of blocks in the block diagrams, may be implemented atleast partially by computer program instructions. These computer programinstructions may be loaded onto a general purpose computer, specialpurpose computer, special purpose hardware-based computer, or otherprogrammable data processing apparatus to produce a machine, such thatthe instructions which execute on the computer or other programmabledata processing apparatus create means for implementing thefunctionality of at least some of the blocks of the block diagrams, orcombinations of blocks in the block diagrams discussed.

These computer program instructions may also be stored in anon-transitory computer-readable memory that can direct a computer orother programmable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including instruction meansthat implement the function specified in the block or blocks. Thecomputer program instructions may also be loaded onto a computer orother programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer or other programmableapparatus to produce a computer implemented process such that theinstructions that execute on the computer or other programmableapparatus provide task, acts, actions, or operations for implementingthe functions specified in the block or blocks.

One or more components of the systems and one or more elements of themethods described herein may be implemented through an applicationprogram running on an operating system of a computer. They may also bepracticed with other computer system configurations, including hand-helddevices, multiprocessor systems, microprocessor-based or programmableconsumer electronics, mini-computers, mainframe computers, and the like.

Application programs that are components of the systems and methodsdescribed herein may include routines, programs, components, datastructures, etc. that may implement certain abstract data types andperform certain tasks or actions. In a distributed computingenvironment, the application program (in whole or in part) may belocated in local memory or in other storage. In addition, oralternatively, the application program (in whole or in part) may belocated in remote memory or in storage to allow for circumstances wheretasks can be performed by remote processing devices linked through acommunications network.

Although only a few exemplary embodiments have been described in detailherein, those skilled in the art will readily appreciate that manymodifications are possible in the exemplary embodiments withoutmaterially departing from the novel teachings and advantages of theembodiments of the present disclosure. Accordingly, all suchmodifications are intended to be included within the scope of theembodiments of the present disclosure as defined in the followingclaims.

What is claimed is:
 1. A method of controlling fuel supply to aplurality of gas turbine engines associated with a hydraulic fracturingsystem, the method comprising: (a) receiving a signal indicating thatsupply pressure of primary fuel to one or more gas turbine engines ofthe plurality of gas turbine engines falls below a set point; (b) basedat least in part on the signal: initiating a timer; and increasing adata sampling rate associated with the plurality of gas turbine engines;(c) determining that the supply pressure of primary fuel to the one ormore gas turbine engines remains below the set point when the timerreaches a predetermined end time; (d) identifying a gas turbine engineof the plurality of gas turbine engines operating on primary fuel havinga highest amount of secondary fuel available; and (e) causing supply ofsecondary fuel to the identified gas turbine engine in place of at leastsome of the primary fuel supplied to the identified gas turbine engine.2. The method of claim 1, further comprising repeating steps (a), (b),(c), (d), and (e) for at least some gas turbine engines still operatingusing primary fuel.
 3. The method of claim 1, further comprising:receiving a second signal indicating that supply pressure of primaryfuel to the one or more gas turbine engines rises above a second setpoint; based at least in part on the second signal, initiating a secondtimer; determining that the supply pressure of primary fuel to the oneor more gas turbine engines remains above the second set point when thesecond timer reaches a second predetermined end time; and transferringthe one or more gas turbine engines to primary fuel operation.
 4. Themethod of claim 3, further comprising decreasing the data sampling ratefor the one or more gas turbine engines operating on primary fueloperation.
 5. The method of claim 1, wherein the identifying the gasturbine engine of the plurality of gas turbine engines operating onprimary fuel with highest volume of secondary fuel comprises comparinglevel sensor measurements from the plurality of gas turbine engines. 6.The method of claim 1, wherein the increasing the data sampling ratecomprises increasing the data sampling rate by a factor of at least 2.7. The method of claim 1, further comprising: receiving an indication ofsecondary fuel level below a minimum level for one or more gas turbineengines operating on secondary fuel; and shutting down the one or moregas turbine engines operating on secondary fuel.
 8. The method of claim1, further comprising: receiving a measurement of differential pressurefor one or more primary fuel filters associated with each gas turbineengine operating on primary fuel; and when the differential pressureincreases above a predetermined differential pressure, transferring theassociated gas turbine engine from primary fuel operation to secondaryfuel operation.
 9. The method of claim 1, further comprising: receivinga measurement of differential pressure for one or more primary fuelfilters associated with each gas turbine engine operating on primaryfuel.
 10. The method of claim 1, wherein transferring the gas turbineengine from primary fuel operation to secondary fuel operation comprisesgradually closing one or more valves associated with primary fueloperation while gradually opening one or more valves associated withsecondary fuel operation.
 11. A system for controlling fuel supply to aplurality of gas turbine engines associated with a hydraulic fracturingsystem, the system comprising: a plurality of gas turbine enginesassociated with a plurality of pumps; and a controller in communicationwith the plurality of gas turbine engines, the controller comprising amemory with computer-readable instructions operable to: (a) receive asignal indicating when supply pressure of primary fuel to one or moregas turbine engines of the plurality of gas turbine engines falls belowa set point; (b) based at least in part on the signal: initiate a timer;and increase a data sampling rate associated with the plurality of gasturbine engines; (c) determine that the supply pressure of primary fuelto the one or more gas turbine engines remains below the set point whenthe timer reaches a predetermined end time; (d) identify a gas turbineengine of the plurality of gas turbine engines operating on primary fuelwith a highest amount of secondary fuel available; and (e) transfer thegas turbine engine operating on primary fuel with highest amount ofsecondary fuel available from primary fuel operation to secondary fueloperation.
 12. The system of claim 11, wherein the controller further isoperable to repeat steps (a), (b), (c), and (e) for at least some of theother gas turbine engines of the plurality of gas turbine engines. 13.The system of claim 11, wherein each of the plurality of gas turbineengines connects to a pump, and each of the gas turbine engines andconnected pumps comprises a directly-driven turbine fracturing pump. 14.The system of claim 11, wherein the primary fuel comprises a gaseousfuel, and the secondary fuel comprises diesel fuel.
 15. The system ofclaim 11, wherein the controller is further operable to: receive asecond signal indicating that a supply pressure of primary fuel to oneor more gas turbine engines associated with the plurality of gas turbineengines rises above a second set point, based at least in part on thesecond signal, initiate a second timer, determine that the supplypressure of primary fuel to the one or more gas turbine engines remainsabove the second set point when the second timer reaches a secondpredetermined end time, and transfer the one or more gas turbine enginesto primary fuel operation.
 16. The system of claim 15, wherein thecontroller further is operable to decrease the data sampling rate forthe one or more gas turbine engines operating on primary fuel operation.17. The system of claim 11, further comprising: a plurality of secondarysensors configured to generate a secondary signal indicative of anamount of secondary fuel in a secondary fuel supply, and wherein thesecondary sensors comprise one or more of a RADAR level sensor, aguided-wave RADAR level sensor, an ultrasonic level sensor, a capacitivelevel sensor, a hydrostatic level sensor, a probe-type level sensor, afloat-type level sensor, a RF admittance level sensor, or anelectro-optical level sensor.
 18. The system of claim 11, whereinincreasing the data sampling rate comprises increasing the data samplingrate by a factor of at least
 2. 19. The system of claim 11, wherein thecontroller further is operable to: receive a signal indicative of asecondary fuel level below a minimum level for one or more gas turbineengines operating on secondary fuel, and shut down the one or more gasturbine engines operating on secondary fuel.
 20. The system of claim 11,wherein the controller further is operable: to receive a measurement ofdifferential pressure for a primary fuel filter associated with each gasturbine engine operating on primary fuel, and when the differentialpressure increases above a predetermined differential pressure for oneof the gas turbine engines, transfer the one gas turbine engine fromprimary fuel operation to secondary fuel operation.
 21. The system ofclaim 11, wherein the controller comprises one or more of: amicro-controller, a supervisory control and data acquisition (SCADA)system, a computer, a programmable logic controller (PLC), a remoteterminal unit (RTU), or a distributed control system (DCS).
 22. Thesystem of claim 11, wherein the primary fuel is supplied to the one ormore gas turbine engines via one or more: of a hybrid hub system, amultiple hub and spoke system, or a daisy chain system.